Method of forming golf club head assembly

ABSTRACT

A method of forming a golf club head assembly includes aligning a faceplate with a recess of a club head; welding the faceplate to the club head; then, after welding the faceplate, heating the club head and the faceplate to at least a solvus temperature of the faceplate for a predetermined amount of time; and then, after heating the club head and the faceplate, allowing the club head and the faceplate to air cool.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application Ser. No.16/295,716, filed on Mar. 7, 2019, which is a continuation of U.S.patent application Ser. No. 15/829,635, filed on Dec. 1, 2017, andissued as U.S. Pat. No. 10,258,837 on Apr. 16, 2019, which is acontinuation-in-part of U.S. patent application Ser. No. 15/046,132,filed on Feb. 17, 2016, and issued as U.S. Pat. No. 9,938,601 on Apr.10, 2018, which is a continuation-in-part of U.S. patent applicationSer. No. 14/624,488, filed on Feb. 17, 2015, and issued as U.S. Pat. No.9,238,858 on Jan. 19, 2016, which is a continuation-in-part of U.S.patent application Ser. No. 14/228,503, filed on Mar. 28, 2014, andissued as U.S. Pat. No. 9,452,488 on Sep. 27, 2016, which claims thebenefit of U.S. Provisional Patent Application No. 61/941,117, filed onFeb. 18, 2014, the entire contents of which are fully incorporatedherein by reference. U.S. patent application Ser. No. 15/829,635 furtherclaims priority to U.S. Provisional Patent Application No. 62/428,728,filed Dec. 1, 2016, the entire contents of which is fully incorporatedherein by reference. Furthermore, this claims priority to U.S.Provisional Patent Application No. 62/755,343, filed Nov. 2, 2018 and toU.S. Provisional Patent Application No. 62/861,910, filed Jun. 14, 2019,the entire contents of which are fully incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to golf equipment, and moreparticularly, to faceplates of golf club heads and methods tomanufacture and heat treat golf club heads.

BACKGROUND

The present invention relates to golf clubs and particularly to a methodof forming a golf club head assembly. Conventional golf club headassemblies include a faceplate welded to a club head. The faceplate hasa slightly rounded shape in order to provide a straighter and/or longerflight path for a golf ball, even when the ball is struck off-centerwith respect to the faceplate. The faceplate has a bulge dimension, orcurvature from a toe end to a heel end, and a roll dimension, orcurvature from the crown edge to the sole edge. Aspects of the inventionwill become apparent by consideration of the detailed description andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a club head and a face plate.

FIG. 2 is a perspective view of the club head with the face plateremoved.

FIG. 3 is a top view of a club head assembly.

FIG. 4 is a side section view of the club head assembly of FIG. 3 alongsection 4-4.

FIG. 5 is a side view of the club head assembly of FIG. 3.

FIG. 6 is a schematic view of a process for forming a golf club headassembly.

FIG. 7 is a chart showing experimental bulge and roll measurements forfaceplates that are subjected to various heat-treatment processes.

FIG. 8 is a chart showing experimental roll measurements for faceplateshaving various geometries.

FIG. 9 is a chart showing experimental bulge and roll measurements forfaceplates that are subjected to various heat-treatment processes.

FIG. 10 is a chart showing durability measurements for faceplates havingvarious material compositions.

FIG. 11A is a microstructure of non-annealed T9S. FIG. 11B is amicrostructure of annealed T-9S. FIG. 11C is a stress/strain curveshowing unstable yielding of the non-annealed T-9S alloy. FIG. 11D is astress/strain curve showing a more stable yielding of the annealed T-9Salloy.

FIG. 12 is a Ti—Al phase diagram.

FIG. 13 is a chart showing experimental bulge and roll measurements forfaceplates made of Ti 6-4 alloys with and without heat treat and T-9Salloys with heat treat.

FIG. 14 is a phase diagram marked with the position of T-9S and Ti-7S⁺alloys.

FIG. 15 is a chart showing percentage deflection of faceplates made ofTi 6-4 alloy with no heat treat and various T9S alloys having gonethrough differing heat treats after these faceplates have been hit 100and 1000 times.

FIG. 16 is a chart showing experimental bulge and roll measurements forfaceplates made of Ti-7S⁺ alloys with and without heat treat at 650° C.

FIG. 17 is a chart showing experimental bulge and roll measurements forfaceplates made of Ti-7S⁺ alloys with and without heat treat at 700° C.

FIG. 18 is a chart showing percentage deflection of faceplates made ofTi 6-4 alloy with no heat treat, and various T9S and Ti-7S⁺ alloyshaving gone through differing heat treats after these faceplates havebeen hit 100 and 1000 times.

FIG. 19. is a comparative chart showing a plasma weld stress relief heattreatment vs. a laser weld stress relieve heat treatment with T9S alloy.

FIG. 20 is a bar graph showing the bulge and roll percent deflection ofa golf club head having a T9S faceplate with a heat treatment of 600° C.for 1 hour, and a golf club head having T9S with faceplate with a heattreatment of 600° C. for 1 hour+a 30 minute soak or cool down after 50and 250 golf ball impact hits.

FIG. 21 is a bar graph showing the total number of golf ball impact hitsuntil failure as compared between a golf club head having a T9Sfaceplate with a heat treatment of 600° C. for 1 hour, and a golf clubhead having T9S with faceplate with a heat treatment of 600° C. for 1hour+a 30 minute soak or cool down.

FIG. 22 is a phase diagram marked with the position of HST-180 alloysand T-9S alloys.

FIG. 23 is a chart showing experimental bulge and roll measurements forfaceplates made of HST-180 alloys with and without heat treatment of550° C.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” and “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items. All weight percent (wt %) numbers describedbelow are a total weight percent.

DETAILED DESCRIPTION

FIG. 1-3 shows a golf club head 10 and a faceplate 14. In oneembodiment, the golf club head 10 is formed from a cast material and thefaceplate 14 is formed from a rolled material. Further, in theillustrated embodiment, the golf club head 10 is for a metal wooddriver; in other embodiments, the golf club head 10 is for a fairwaywood; in other embodiments, the golf club head 10 is for hybrid clubs;in other embodiments, the golf club head 10 is for an iron club. Theclub head 10 may also include a hosel and a hosel transition (shown as18). For example, the hosel may be located at or proximate to the heelend 34. The hosel may extend from the club head 10 via the hoseltransition 18. To form a golf club, the hosel may receive a first end ofa shaft 20. The shaft 20 may be secured to the golf club head 10 by anadhesive bonding process (e.g., epoxy) and/or other suitable bondingprocesses (e.g., mechanical bonding, soldering, welding, and/orbrazing). Further, a grip (not shown) may be secured to a second end ofthe shaft 20 to complete the golf club.

As shown in FIG. 2, the club head 10 further includes a recess oropening 22 for receiving the faceplate 14. In the illustratedembodiment, the opening 22 includes a lip 26 extending around theperimeter of the opening 22. The faceplate 14 is aligned with theopening and abuts the lip 26. The faceplate 14 is secured to the clubhead 10 by welding, forming a club head assembly 30. In one embodiment,the welding is a pulse plasma welding process.

The faceplate 14 includes a heel end 34 and a toe end 38 opposite theheel end 34. The heel end 34 is positioned proximate the hosel portion(hosel and hosel transition 18) where the shaft 20 (FIG. 1) is coupledto the club head assembly 30. The faceplate 14 further includes a crownedge 42 and a sole edge 46 opposite the crown edge 42. The crown edge 42is positioned adjacent an upper edge of the club head 10, while the soleedge 46 is positioned adjacent the lower edge of the club head 10. Asshown in FIG. 3, the faceplate 14 has a bulge curvature in a directionextending between the heel end 34 and the toe end 38. As shown in FIGS.4 and 5, the faceplate 14 also has a roll curvature in a directionextending between the crown edge 42 and the sole edge 46. In oneembodiment, the faceplate may have a minimum wall thickness of 1.5millimeters, 1.4 millimeters, 1.3 millimeters, 1.2 millimeters, 1.1millimeters, 1.0 millimeters, 0.9 millimeters, 0.8 millimeters, 0.7millimeters, 0.6 millimeters, 0.5 millimeters and 0.4 millimeters. Inone embodiment, the faceplate may have a minimum wall thickness of 0.7millimeters.

The faceplate 14 is formed from a titanium alloy. In one embodiment, thefaceplate 14 is an α-β titanium (α-β Ti) alloy. The α-β Ti alloy maycontain neutral alloying elements such as tin and a stabilizers such asaluminum and oxygen. The α-β Ti alloy may contain β-stabilizers such asmolybdenum, silicon and vanadium. All numbers described below regardingweight percent are a total weight percent (wt %). The total weightpercent of α-stabilizer aluminum in α-β Ti alloy may be between 2 wt %to 10 wt %, 3 wt % to 9 wt %, 4 wt % to 8 wt %, 5 wt % to 7 wt %, 2 wt %to 20 wt %, 3 wt % to 19 wt %, 4 wt % to 18 wt %, 5 wt % to 17 wt %, 6wt % to 16 wt %, 7 wt % to 15 wt %, 8 wt % to 14 wt %, 9 wt % to 13 wt%, 10 wt % to 12 wt %, 7 wt % to 9 wt %, 7 wt % to 10 wt %, 7 wt % to 11wt %, 7 wt % to 12 wt %, 7 wt % to 13 wt %, 7 wt % to 14 wt %, 7 wt % to15 wt %, 7 wt % to 16 wt %, 7 wt % to 17 wt %, 7 wt % to 18 wt %, 7 wt %to 19 wt %, 7 wt % to 20 wt %, 8 wt % to 10 wt %, 8 wt % to 11 wt %, 8wt % to 12 wt %, 8 wt % to 13 wt %, 8 wt % to 14 wt %, 8 wt % to 15 wt%, 8 wt % to 16 wt %, 8 wt % to 17 wt %, 8 wt % to 18 wt %, 8 wt % to 19wt %, 8 wt % to 20 wt %, 9 wt % to 11 wt %, 9 wt % to 12 wt %, 9 wt % to13 wt %, 9 wt % to 14 wt %, 9 wt % to 15 wt %, 9 wt % to 16 wt %, 9 wt %to 17 wt %, 9 wt % to 18 wt %, 9 wt % to 19 wt %, 9 wt % to 20 wt %, 10wt % to 13 wt %, 10 wt % to 14 wt %, 10 wt % to 15 wt %, 10 wt % to 16wt %, 10 wt % to 17 wt %, 10 wt % to 18 wt %, 10 wt % to 19 wt %, 10 wt% to 20 wt %, 11 wt % to 13 wt %, 11 wt % to 14 wt %, 11 wt % to 15 wt%, 11 wt % to 16 wt %, 11 wt % to 17 wt %, 11 wt % to 18 wt %, 11 wt %to 19 wt %, 11 wt % to 20 wt %, 12 wt % to 14 wt %, 12 wt % to 15 wt %,12 wt % to 16 wt %, 12 wt % to 17 wt %, 12 wt % to 18 wt %, 12 wt % to19 wt %, 12 wt % to 20 wt %, 13 wt % to 15 wt %, 13 wt % to 16 wt %, 13wt % to 17 wt %, 13 wt % to 18 wt %, 13 wt % to 19 wt %, 13 wt % to 20wt %, 14 wt % to 16 wt %, 14 wt % to 17 wt %, 14 wt % to 18 wt %, 14 wt% to 19 wt %, 14 wt % to 20 wt %, 15 wt % to 17 wt %, 15 wt % to 18 wt%, 15 wt % to 19 wt %, 15 wt % to 20 wt %, 16 wt % to 18 wt %, 16 wt %to 19 wt %, 16 wt % to 20 wt %, 17 wt % to 19 wt %, 17 wt % to 20 wt %,or 18 wt % to 20 wt %. In certain embodiments, the total weight percentof α-stabilizer aluminum in α-β Ti alloy may be between 7 wt % to 13 wt%, 8 wt % to 13 wt %, 9 wt % to 13 wt %, 10 wt % to 13 wt %, 11 wt % to13 wt %, or 12 wt % to 13 wt %. The total weight percent of α-stabilizeroxygen in α-β Ti alloy may be between 0.05 wt % to 0.35 wt %, or 0.10 wt% to 0.20 wt %. The total weight percent of β-stabilizer molybdenum inα-β Ti alloy may be between 0.2 wt % to 1.0 wt %, or 0.6 wt % to 0.8 wt%, or trace amounts. The total weight percent of β-stabilizer vanadiumin α-β Ti alloy may be between 1.5 wt % to 7 wt %, or 3.5 wt % to 4.5 wt%. The total weight percent of β-stabilizer silicon in α-β Ti alloy maybe between 0.01 to 0.10 wt %, or 0.03 wt % to 0.07 wt %. The α-β Tialloy may be Ti-6Al-4V (or Ti 6-4), Ti-7S⁺ (or Ti-7S, T-7S, or ST721),Ti-9S (or T-9S), Ti-662, Ti-8-1-1, Ti-65K, Ti-6246, Ti-7S, or IMI 550.The combination of α, β stabilizers allows the α-β Ti alloys to be heattreated.

In one embodiment, after welding the faceplate 14 to the club head 10,the club head 10 and faceplate 14 may be heated to a temperature at,just above, or greater than the solvus temperature of the faceplate fora predetermined amount of time. In another embodiment, after welding thefaceplate 14 to the club head 10, the club head assembly 30 may be heattreated at a temperature at, just above or greater than the α-β Tisolvus temperature for a predetermined amount of time. In anotherembodiment, after welding the faceplate 14 to the club head 10, the clubhead assembly 30 may be heat treated at a temperature at, just above orgreater than the α-β Ti solvus temperature for a predetermined amount oftime. Also, during this step, an inert gas may be pumped into theheating chamber housing the club head assembly 30 to remove all oxygenover a predetermined amount of time discussed below. Upon cooling of theclub head assembly 30 as discussed below, additional inert gas may bepumped back into the chamber where the club head assembly 30 is allowedto cool to room temperature.

As discussed above, after heating the club head assembly 30 (or the clubhead 10 and the welded faceplate 14), the club head assembly 30 isallowed to cool to room temperature. In another embodiment, after theheat treatment, the club head assembly 30 may be allowed to air cool toslowly reduce the club head assembly's temperature. The cooling of theclub head assembly 30 may be done in an inert gas environment ornon-contained environment (open air). In another embodiment, the clubhead assembly 30 may be allowed to cool in inert gas to slowly reducethe club head assembly's temperature and reduce chance for oxidation.The inert gas may be selected from the group consisting of nitrogen (N),argon (Ar), helium (He), neon (Ne), krypton (Kr), and xenon (Xe) or acompound gas thereof. After heating to, just above, or greater than theα-β Ti solvus temperature, inert gas may be pumped back into a chamberunder vacuum housing the club assembly 30, which ensures no oxygen ispresent to prevent oxidation to the titanium faceplate 14 and club headsurfaces 10.

As understood by a person of ordinary skill, the solvus temperature foran alloy is the temperature barrier at which smaller constituentmolecules dissolve within the general matrix of the material and becomemore mobile. The solvus temperatures of most α-β Ti alloys are verifiedand readily available in academic literature or information published bymaterial suppliers. If published data is unavailable, the temperaturevalues can be estimated and experimentally confirmed, since it isdependent on the material's chemistry. The solvus temperature for α-β Tican be above 400° C. and below 600° C., above 400° C. and below 1180° C.In certain embodiments, the solvus temperature for α-β Ti alloy can bebetween 500° C. and 1030° C., 680° C. and 1030° C., 760° C. and 1030°C., 870° C. and 1030° C., 895° C. and 1030° C., or 960° C. and 1030° C.

In one embodiment, the α-β Ti may be Ti 6-4 containing 6 wt % aluminum(Al), and 4 wt % vanadium (V), with the remaining alloy compositionbeing titanium and possibly some trace elements. In some embodiments, Ti6-4 contains between 5.5 wt %-6.75 wt % Al, between 3.5 wt %-4.5 wt % V,a maximum of 0.08 wt % carbon (C), a maximum of 0.03 wt % silicon (Si),a maximum of 0.3 wt % iron (Fe), a maximum of 0.2 wt % oxygen (O), amaximum of 0.015 wt % tin (Sn), and trace amounts of molybedenum (Mo),with the remaining alloy composition being titanium. In someembodiments, Ti 6-4 contains between 5.5 wt %-6.75 wt % Al, between 3.5wt %-4.5 wt % V, 0.08 wt % or less carbon (C), 0.03 wt % or less silicon(Si), 0.3 wt % or less iron (Fe), 0.2 wt % or less oxygen (O), 0.015 wt% or less tin (Sn), and trace amounts of molybedenum (Mo), with theremaining alloy composition being titanium. Ti 6-4 is a grade 5titanium. The solvus temperature for Ti 6-4 is between 540° C. and 560°C. In some embodiments, Ti 6-4 has a density of 0.1597 lb/in³ (4.37g/cc). Ti-6-4 may also be designated as T-65K.

In one embodiment, the α-β Ti may be Ti-7S⁺ (or Ti-7S, T-7S, or ST721),containing between 7-8 wt % aluminum (Al), between 2-3 wt % molybdenum(Mo), between 0.5-1.5 wt % iron (Fe), between 0.5-1.5 wt % vanadium(Vn), with the remaining alloy composition being titanium and othertrace elements. In one embodiment, the α-β Ti may be Ti-7S⁺ (or Ti-7S,T-7S, or ST721), containing between 7-20 wt % aluminum (Al), between1.5-5.0 wt % molybdenum (Mo), between 0.3-2.0 wt % iron (Fe), between0.3-2.0 wt % vanadium (Vn), with the remaining alloy composition beingtitanium and other trace elements. In some embodiments, trace elementsof the optimized titanium alloy comprising Ti-7S⁺ can include 0.25 wt %silicon or less, 0.20 wt % oxygen or less, 0.05 wt % carbon or less, and0.04 wt % nitrogen or less. The solvus temperature for Ti-7S⁺ may bebetween 720° C. and 760° C. The solvus temperature for Ti-7S⁺ may be740° C. In this example, the density of Ti 7S is 0.162 lb/in³ (4.47g/cm³).

In other embodiments, the golf club head 10 may be another α-β Ti alloy,such as Ti-9S (or T-9S), which contains 8 wt % Al, 1 wt % V, and 0.2 wt% Si, with the remaining alloy composition being titanium and possiblysome trace elements. In some embodiments, Ti-9S (or T-9S) contains 6.5wt %-8.5 wt % Al, between 1 wt %-2 wt % V, a maximum of 0.08 wt % C, amaximum of 0.2 wt % Si, a maximum of 0.3 wt % Fe, a maximum of 0.2 wt %O, a maximum of 0.05 wt % N, trace amounts of Mo, and trace amounts ofSn, with the remaining alloy composition being titanium. In someembodiments, Ti-9S (or T-9S) contains 6.5 wt %-8.5 wt % Al, between 1 wt%-2 wt % V, less than 0.1 wt % C, a maximum of 0.2 wt % Si, a maximum of0.4 wt % Fe, a maximum of 0.15 wt % O, less than 0.05 wt % N, traceamounts of Mo, and trace amounts of Sn, with the remaining alloycomposition being titanium. In some embodiments, Ti-9S (or T-9S)contains 6.5 wt %-8.5 wt % Al, between 1 wt %-2 wt % V, 0.1 wt % or lessC, 0.2 wt % or less Si, 0.4 wt % or less Fe, 0.15 wt % or less O, lessthan 0.05 wt % N, trace amounts of Mo, and trace amounts of Sn, with theremaining alloy composition being titanium. The solvus temperature forTi-9S (or T-9S) is between 560° C. and 590° C. In some embodiments, theTi-9S (or T-9s) will have higher porosity and a lower yield than Ti8-1-1. Ti-9S (or T-9S) has a density of about 0.156 lb/in³ to 0.157lb/in³ (4.32-4.35 g/cc). Ti-9S (or T-9S) has a density of 0.156 lb/in³(4.32 g/cc).

In other embodiments, the material may be another α-β Ti alloy, such asTi-6-6-2, Ti-6246, or IMI 550. Titanium 662 may contain 6 wt % Al, 6 wt% V, and 2 wt % Sn, with the remaining alloy composition being titaniumand possibly some trace elements. Ti-6-6-2 has a density of 0.164 lb/in3(4.54 g/cc). The solvus temperature for Ti 662 is between 540° C. and560° C. Titanium 6246 may contain 6 wt % Al, 2 wt % Sn, 4 wt % zirconium(Zr), and 6 wt % Mo, with the remaining alloy composition being titaniumand possibly some trace elements. The solvus temperature for Ti 6246 isbetween 570° C. and 590° C. Ti-6246 has a density of 0.168 lb/in3 (4.65g/cc). IMI 550 may contain 6 wt % Al, 2 wt % Sn, 4 wt % Mo, and 0.5 wt %Si, with the remaining alloy composition being titanium and possiblysome trace elements. The solvus temperature for IMI 550 is between 490°C. and 510° C. IMI 550 has a density of 0.157 lb/in³ (4.60 g/cc).

In other embodiments, the material may be another α-β Ti alloy, such asTi-8-1-1, which may contain 8 wt % Al, 1.0 wt % Mo, and 1 wt % V, withthe remaining alloy composition being titanium and possibly some traceelements. In some embodiments, Ti-8-1-1 may contain 7.5 wt %-8.5 wt %Al, 0.75 wt %-1.25 wt % Mo., 0.75 wt %-1.25 wt % V, a maximum of 0.08 wt% C, a maximum of 0.3 wt % Fe, a maximum of 0.12 wt % O, a maximum of0.05 wt % N, a maximum of 0.015 wt % H, a maximum of 0.015 wt % Sn, andtrace amounts of Si, with the remaining alloy composition beingtitanium. The solvus temperature for Ti-8-1-1 is between 560° C. and590° C. In some embodiments, Ti-8-1-1 has a density of 0.1580 lb/in³(4.37 g/cc).

In other embodiments, the material may be another α-β Ti alloy, such asHST-180, which may contain between 4-20 wt % Al, 2-3 wt % Fe, 0.01-0.10wt % Si, with the remaining alloy composition being titanium andpossibly some trace elements. In some embodiments, HST-180 may comprise4-18 wt % Al, 5-7 wt % Al, or any other suitable wt % Al listed abovefor the α-β titanium (α-β Ti) alloy. In some embodiments, HST-180 mayfurther comprise less than 0.25 wt % silicon (Si), less than 0.05 wt %carbon (C), less than 0.05 wt % copper (Cu), less than 0.05 wt %molybdenum (Mo), and less than 0.05 wt % vanadium (V) and the remainingweight percent is titanium (Ti). In some embodiments, HST-180 mayfurther comprise less than 0.08 wt % silicon (Si), less than 0.02 wt %carbon (C), less than 0.02 wt % copper (Cu), less than 0.02 wt %molybdenum (Mo), and less than 0.02 wt % vanadium (V) and the remainingweight percent is titanium (Ti).

In some embodiments, HST-180 may contain 6-7 wt % Al, 2-3 wt % Fe, amaximum of 0.01 wt % C, a maximum of 0.06 wt % Si, a maximum of 0.01 wt% Cu, a maximum of 0.01 wt % Mo, a maximum of 0.01 wt % V, with theremaining alloy composition being titanium. The solvus temperature forHST-180 is between 535° C. and 545° C. In some embodiments, HST-180 hasa density of 0.1759 lb/in³ (4.37 g/cc).

In other embodiments, the material may be another α-β Ti alloy which maycontain 7 wt %-8 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 500° C. and 720° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 8 wt %-9 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 680° C. and 810° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 9 wt %-10 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 760° C. and 895° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 10 wt %-11 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 870° C. and 910° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 11 wt %-12 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 890° C. and 980° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 12 wt %-13 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 960° C. and 1030° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 13 wt %-14 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 980° C. and 1070° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 14 wt %-15 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 1030° C. and 1100° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 16 wt %-17 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 1100° C. and 1140° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 17 wt %-18 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 1140° C. and 1150° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 18 wt %-19 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 1150° C. and 1180° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 19 wt %-20 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 1170° C. and 1180° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 7 wt %-13 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 500° C. and 1030° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 8 wt %-13 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 680° C. and 1030° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 9 wt %-13 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 760° C. and 1030° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 10 wt %-13 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 870° C. and 1030° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 11 wt %-13 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 890° C. and 1030° C.

In other embodiments, the material may be another α-β Ti alloy which maycontain 12 wt %-13 wt % Al with the remaining alloy composition beingtitanium and other α- and β-stabilizers. The solvus temperature for thisα-β Ti is between 960° C. and 1030° C.

FIG. 6 shows the process for forming for the club head assembly 30. Inthe first step 62, the faceplate 14 is aligned with respect to the clubhead 10. The second step 66 involves welding the faceplate 14 to theclub head 10. In the third step 70, the club head 10 and the faceplate14 are heated to a temperature at or above the solvus temperature of thefaceplate 14 material. Finally, in the fourth step 74 the club head 10and the faceplate 14 are air cooled.

In one embodiment, the club head assembly 30 is heat treated at atemperature at or above the solvus temperature of the α-β Ti alloy forbetween 1 hour and 6 hours in the third step 70. In one embodiment, theclub head assembly 30 is heat treated at a temperature at or above thesolvus temperature of the α-β Ti alloy for between 1 hour and 2 hours inthe third step 70. In one embodiment, the club head assembly 30 is heattreated at a temperature at or above the solvus temperature of the α-βTi alloy for between 1 hour and 4 hours in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureat or above the solvus temperature of the α-β Ti alloy for between 4hours and 6 hours in the third step 70. In one embodiment, the club headassembly 30 is heat treated at a temperature at or above the solvustemperature of the α-β Ti alloy for between 1.5 hours and 5.5 hours inthe third step 70. In one embodiment, the club head assembly 30 is heattreated at a temperature at or above the solvus temperature of the α-βTi alloy for between 2 hours and 5 hours in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureat or above the solvus temperature of the α-β Ti alloy for between 2.5hours and 4.5 hours in the third step 70. In one embodiment, the clubhead assembly 30 is heat treated at a temperature at or above the solvustemperature of the α-β Ti alloy for between 3 hours and 4 hours in thethird step 70.

In one embodiment, the club head assembly 30 is heat treated at atemperature at or above the solvus temperature of the α-β Ti alloy forat least 1 hour in the third step 70. In one embodiment, the club headassembly 30 is heat treated at a temperature at or above the solvustemperature of the α-β Ti alloy for at least 1.5 hours in the third step70. In one embodiment, the club head assembly 30 is heat treated at atemperature at or above the solvus temperature of the α-β Ti alloy forat least 2 hours in the third step 70. In one embodiment, the club headassembly 30 is heat treated at a temperature at or above the solvustemperature of the α-β Ti alloy for at least 2.5 hours in the third step70. In one embodiment, the club head assembly 30 is heat treated at atemperature at or above the solvus temperature of the α-β Ti alloy forat least 3 hours in the third step 70. In one embodiment, the club headassembly 30 is heat treated at a temperature at or above the solvustemperature of the α-β Ti alloy for at least 3.5 hours in the third step70. In one embodiment, the club head assembly 30 is heat treated at atemperature at or above the solvus temperature of the α-β Ti alloy forat least 4 hours in the third step 70. In one embodiment, the club headassembly 30 is heat treated at a temperature at or above the solvustemperature of the α-β Ti alloy for at least 4.5 hours in the third step70. In one embodiment, the club head assembly 30 is heat treated at atemperature at or above the solvus temperature of the α-β Ti alloy forat least 5 hours in the third step 70. In one embodiment, the club headassembly 30 is heat treated at a temperature at or above the solvustemperature of the α-β Ti alloy for at least 5.5 hours in the third step70. In one embodiment, the club head assembly 30 is heat treated at atemperature at or above the solvus temperature of the α-β Ti alloy forat least 6 hours in the third step 70.

In one embodiment, the club head assembly 30 is heat treated between400° C. and 630° C., between 400° C. and 1200° C., or between 500° C.and 1030° C. in the third step 70. In one embodiment, the club headassembly 30 is heat treated between 425° C. and 550° C., between 425° C.and 1200° C., or between 525° C. and 1030° C. In one embodiment, theclub head assembly 30 is heat treated between 450° C. and 525° C.,between 450° C. and 1095° C., or between 550° C. and 925° C. in thethird step 70. In one embodiment, the club head assembly 30 is heattreated between 550° C. and 625° C., between 550° C. and 1195° C., orbetween 650° C. and 925° C. in the third step 70. In one embodiment, theclub head assembly 30 is heat treated between 520° C. and 1200° C. inthe third step 70. In one embodiment, the club head assembly 30 is heattreated between 620° C. and 1150° C. in the third step 70. In oneembodiment, the club head assembly 30 is heat treated between 720° C.and 1000° C. in the third step 70. In one embodiment, the club headassembly 30 is heat treated between 820° C. and 950° C. in the thirdstep 70. In one embodiment, the club head assembly 30 is heat treatedbetween 720° C. and 900° C. in the third step 70. In one embodiment, theclub head assembly 30 is heat treated between 820° C. and 850° C. in thethird step 70. In one embodiment, the club head assembly 30 is heattreated at 400° C., 410° C., 420° C., 430° C., 440° C., 450° C., 460°C., 470° C., 480° C., 490° C., 500° C., 510° C., 520° C., 530° C., 540°C., 550° C., 560° C., 570° C., 580° C., 590° C., 600° C., 610° C., 620°C., 630° C., 640° C., 650° C., 660° C., 670° C., 680° C., 690° C., 700°C., 710° C., 720° C., 730° C., 740° C., 750° C., 760° C., 770° C., 780°C., 790° C., 800° C., 810° C., 820° C., 830° C., 840° C., 850° C., 860°C., 870° C., 880° C., 890° C., 900° C., 910° C., 920° C., 930° C., 940°C., 950° C., 960° C., 970° C., 980° C., 990° C., 1000° C., 1010° C.,1020° C., 1030° C., 1040° C., 1050° C., 1060° C., 1070° C., 1080° C.,1090° C., 1100° C., 1110° C., 1120° C., 1130° C., 1140° C., 1150° C.,1160° C., 1170° C., 1180° C., 1190° C., or 1200° C. in the third step 70for 30 minutes, 60 minutes, 90 minutes, 120 minutes, 150 minutes, 180minutes, 210 minutes, 240 minutes, 270 minutes, 300 minutes, 330 minutesor 360 minutes.

In one embodiment, the club head assembly 30 is heat treated at atemperature of at least 400° C. in the third step 70. In one embodiment,the club head assembly 30 is heat treated at a temperature of at least420° C. in the third step 70. In one embodiment, the club head assembly30 is heat treated at a temperature of at least 440° C. in the thirdstep 70. In one embodiment, the club head assembly 30 is heat treated ata temperature of at least 460° C. in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureof at least 475° C. in the third step 70. In one embodiment, the clubhead assembly 30 is heat treated at a temperature of at least 480° C. inthe third step 70. In one embodiment, the club head assembly 30 is heattreated at a temperature of at least 500° C. in the third step 70. Inone embodiment, the club head assembly 30 is heat treated at atemperature of at least 520° C. in the third step 70. In one embodiment,the club head assembly 30 is heat treated at a temperature of at least540° C. in the third step 70. In one embodiment, the club head assembly30 is heat treated at a temperature of at least 560° C. in the thirdstep 70. In one embodiment, the club head assembly 30 is heat treated ata temperature of at least 575° C. in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureof at least 580° C. In one embodiment, the club head assembly 30 is heattreated at a temperature of at least 600° C. in the third step 70. Inone embodiment, the club head assembly 30 is heat treated at atemperature of at least 620° C. in the third step 70. In one embodiment,the club head assembly 30 is heat treated at a temperature of at least625° C. in the third step 70. In one embodiment, the club head assembly30 is heat treated at a temperature of at least 630° C. in the thirdstep 70. In one embodiment, the club head assembly 30 is heat treated ata temperature of at least 640° C. in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureof at least 660° C. in the third step 70. In one embodiment, the clubhead assembly 30 is heat treated at a temperature of at least 675° C. inthe third step 70. In one embodiment, the club head assembly 30 is heattreated at a temperature of at least 680° C. in the third step 70. Inone embodiment, the club head assembly 30 is heat treated at atemperature of at least 700° C. in the third step 70. In one embodiment,the club head assembly 30 is heat treated at a temperature of at least720° C. in the third step 70. In one embodiment, the club head assembly30 is heat treated at a temperature of at least 740° C. in the thirdstep 70. In one embodiment, the club head assembly 30 is heat treated ata temperature of at least 760° C. in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureof at least 775° C. in the third step 70. In one embodiment, the clubhead assembly 30 is heat treated at a temperature of at least 780° C. inthe third step 70. In one embodiment, the club head assembly 30 is heattreated at a temperature of at least 800° C. in the third step 70. Inone embodiment, the club head assembly 30 is heat treated at atemperature of at least 820° C. in the third step 70. In one embodiment,the club head assembly 30 is heat treated at a temperature of at least840° C. in the third step 70. In one embodiment, the club head assembly30 is heat treated at a temperature of at least 860° C. in the thirdstep 70. In one embodiment, the club head assembly 30 is heat treated ata temperature of at least 875° C. in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureof at least 880° C. in the third step 70. In one embodiment, the clubhead assembly 30 is heat treated at a temperature of at least 900° C. inthe third step 70. In one embodiment, the club head assembly 30 is heattreated at a temperature of at least 920° C. in the third step 70. Inone embodiment, the club head assembly 30 is heat treated at atemperature of at least 940° C. in the third step 70. In one embodiment,the club head assembly 30 is heat treated at a temperature of at least960° C. in the third step 70. In one embodiment, the club head assembly30 is heat treated at a temperature of at least 975° C. in the thirdstep 70. In one embodiment, the club head assembly 30 is heat treated ata temperature of at least 980° C. in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureof at least 1000° C. in the third step 70. In one embodiment, the clubhead assembly 30 is heat treated at a temperature of at least 1020° C.in the third step 70. In one embodiment, the club head assembly 30 isheat treated at a temperature of at least 1040° C. in the third step 70.In one embodiment, the club head assembly 30 is heat treated at atemperature of at least 1060° C. in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureof at least 1075° C. in the third step 70. In one embodiment, the clubhead assembly 30 is heat treated at a temperature of at least 1080° C.in the third step 70. In one embodiment, the club head assembly 30 isheat treated at a temperature of at least 1100° C. in the third step 70.In one embodiment, the club head assembly 30 is heat treated at atemperature of at least 1120° C. in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureof at least 1140° C. in the third step 70. In one embodiment, the clubhead assembly 30 is heat treated at a temperature of at least 1160° C.in the third step 70. In one embodiment, the club head assembly 30 isheat treated at a temperature of at least 1175° C. in the third step 70.In one embodiment, the club head assembly 30 is heat treated at atemperature of at least 1180° C. in the third step 70. In oneembodiment, the club head assembly 30 is heat treated at a temperatureof at least 1200° C. in the third step 70.

In one embodiment, the club head assembly 30 is heat treated between475° C. and 500° C. for between 4 hours and 6 hours in the third step70. In another embodiment, the club head is heat treated between 575° C.and 625° C. for between 1 hour and 2 hours in the third step 70. Inanother embodiment, the club head is heat treated at about 550° C. forbetween 1 hour and 4 hours. In other embodiments, the face plate 14 maybe formed from a different alloy in the third step 70. In otherembodiments, the heat treatment process may be implemented at othertemperatures for a different amount of time. In addition, the heattreatment may be applied to a variety of materials and a variety ofweld-types.

Unlike conventional club head metal aging processes that occur at lowtemperature, heat-treating the club head assembly 30 above the solvustemperature after welding the faceplate 14 relieves stresses in thefaceplate 14 and between the weld and the metal matrix of the club head10. The post-weld stress relief disperses stresses associated with theweld-metal heat affected zone (HAZ), or the area around the weld inwhich the material properties have been altered due to the weldingprocess. Because of the stark contrast in mechanical properties betweenthe HAZ and the rest of the metal matrix, the HAZ is much more likely toexperience a crack and fail. Previous post-weld treatments wereperformed below the solvus temperature for a short duration of time.These processes simply aged the metals, but did not address theincreased stresses transferred to the weld area. Furthermore, thefaceplate was not sufficiently strong and would flatten or lose itscurvature relatively quickly. In contrast, the heat treatment above thesolvus temperature disperses stresses in the weld metal HAZ. Theheat-treatment improves the durability of the HAZ by relieving thestresses. In addition, heat-treating the club head assembly 30 above thesolvus temperature reduces the possibility of generatingtitanium-aluminum (Ti₃Al) crystals along the weld.

The grains of the faceplate alloy may be aligned in a crown to soleorientation prior to heat treating. The crown to sole orientation of thealloy grains permits stretching in the same direction. In someembodiments, the grains of the faceplate α-β titanium (α-β Ti) alloy maybe aligned in a crown to sole orientation prior to heat treating. Thecrown to sole orientation of the α-β Ti alloy grains permits stretchingin the same direction. In some embodiments, the grains of the faceplatedisclosed α-β Ti alloys (e.g., Ti-6Al-4V (or Ti 6-4), Ti-7S⁺ (or Ti-7S,T-7S, or ST721), Ti-9S (or T-9S), Ti-662, Ti-8-1-1, Ti-65K, Ti-6246, andIMI 550alloy) may be aligned in a crown to sole orientation prior toheat treating. The crown to sole orientation of the disclosed α-β Tialloys (e.g., Ti-6Al-4V (or Ti 6-4), Ti-7S⁺ (or Ti-7S, T-7S, or ST721),Ti-9S (or T-9S), Ti-662, Ti-8-1-1, Ti-65K, Ti-6246, or IMI 550 alloy)grains permits stretching in the same direction.

The heat treatment also improves the toughness or durability of thefaceplate 14. The improved toughness permits the faceplate 14 to be madethinner without sacrificing durability, thereby reducing club headweight. The reduced weight of faceplate 14 shifts the center of gravityof the club head assembly 30, and allows additional weight to be addedto another component of the club to further adjust the center ofgravity. Increasing the durability of the faceplate 14 permits thefaceplate 14 to endure a significantly higher number of hits against agolf ball and maintain the faceplate's slightly bowed or rounded shapeover the life of the club while sustaining hundreds or thousands of golfball strikes. Therefore, the club is more forgiving when a ball isstruck off-center because the rounded shape of the faceplate 14 providesa “gear effect” between the ball and faceplate 14.

As shown in FIG. 7, an experiment was performed to compare the effect ofvarious heat treatment temperatures on the faceplate 14 over the courseof 2,000 hits or ball strikes. The faceplates 14 were formed from Ti-9S(or T-9S) alloy. One club head assembly was heated to 400° C., which isbelow the solvus temperature of the Ti-9S (or T-9S) alloy. A second clubhead assembly was heated to 600° C., which is above the solvustemperature of the Ti-9S (or T-9S) alloy. The measurement data providedin FIG. 7 represent the percent change in the radius of curvature of thebulge and the roll dimensions compared to the original radius curvature.As the faceplate becomes more flat, the radius of curvature increases.The club head assembly having a faceplate 14 with Ti-9S treated at 400°C. flattened significantly in both its roll and bulge dimensions within25 hits on a golf ball. In contrast, the club head assembly having aTi-9S faceplate treated at 600° C. maintained its curvaturesignificantly better than the first club head assembly after 2,000 hits.The Ti-9S faceplate treated at 600° C. maintained its curvature in bothbulge and roll dimensions better after 2,000 hits than the first clubhead assembly having a faceplate 14 of untreated Ti-6-4.

For heat treatments below the solvus temperature (for example, at 400°C.), Ti₃Al particles become more mobile and can precipitate into theα-matrix. Some of the Ti₃Al particles gather at grain boundaries and ageharden the material. In contrast, for heat treatments above the solvustemperature (for example, at 600° C.), Ti₃Al particles instead dissolvewithin the α-matrix. The brittle Ti₃Al particles can act as points ofstress. Dissolving brittle Ti₃Al particles within the α-matrix therebyacts as a stress relief. This “stress relief” process enables the clubhead assembly 30 to better withstand tensile and compressive forcesduring impact against a golf ball.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S) remainswithin 2% deflection of its original bulge and roll curvature afterabout 25 strikes. In one embodiment, the faceplate 14 that is formedfrom Ti 6-4 and heat treated above the solvus temperature of Ti 6-4remains within 3% deflection of its original roll curvature and within8% deflection of its original bulge curvature after about 25 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S) remainswithin 8% deflection of its original bulge and roll curvature afterabout 50 strikes. In one embodiment, the faceplate 14 that is formedfrom Ti 6-4 and heat treated above the solvus temperature of Ti 6-4remains within 5% deflection of its original roll curvature and within10% deflection of its original bulge curvature after about 50 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S) remainswithin 10% deflection of its original bulge and roll curvature afterabout 75 strikes. In one embodiment, the faceplate 14 that is formedfrom Ti 6-4 and heat treated above the solvus temperature of Ti 6-4remains within 13% deflection of its original roll curvature and within10% deflection of its original bulge curvature after about 75 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S) remainswithin 10% deflection of its original bulge and roll curvature afterabout 100 strikes. In one embodiment, the faceplate 14 that is formedfrom Ti 6-4 and heat treated above the solvus temperature of Ti 6-4remains within 14% deflection of its original roll curvature and within10% deflection of its original bulge curvature after about 100 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S) remainswithin 10% deflection of its original bulge and roll curvature afterabout 150 strikes. In one embodiment, the faceplate 14 that is formedfrom Ti 6-4 and heat treated above the solvus temperature of Ti 6-4remains within 15% deflection of its original roll curvature and within11% deflection of its original bulge curvature after about 150 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S) remainswithin 10% deflection of its original bulge and roll curvature afterabout 300 strikes. In one embodiment, the faceplate 14 that is formedfrom Ti 6-4 and heat treated above the solvus temperature of Ti 6-4remains within 15% deflection of its original roll and bulge curvatureafter about 300 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S) remainswithin 10% deflection of its original bulge and roll curvature afterabout 1,000 strikes. In one embodiment, the faceplate 14 that is formedfrom Ti 6-4 and heat treated above the solvus temperature of Ti 6-4remains within 23% deflection of its original roll curvature and within17% deflection of its original bulge curvature after about 1,000strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S) remainswithin 10% deflection of its original bulge and roll curvature afterabout 2,000 strikes. In one embodiment, the faceplate 14 that is formedfrom Ti 6-4 and heat treated above the solvus temperature of Ti 6-4remains within 24% deflection of its original roll curvature and within18% deflection of its original bulge curvature after about 2,000strikes.

As shown in FIG. 16, an experiment was performed to compare the effectof various heat treatment temperatures on the faceplate 14 over thecourse of 2,000 hits or ball strikes. However, the data presented inFIG. 16 is limited to the first 175 hits or ball strikes wherein themajority of the changes take place. The data between 175 and 2,000 hitsor ball strikes plateaus and follows a similar progression as the datadisplayed for 50 to 175 hits. The faceplates 14 were formed from Ti-7S⁺(or Ti-7S, T-7S, or ST721—hereafter Ti-7S⁺) alloy. One club headassembly was not heat treated. A second club head assembly was heated to650° C., which is above the solvus temperature of the Ti-7S⁺ alloy. Themeasurement data provided in FIG. 16 represent the percent change in theradius of curvature of the bulge and the roll dimensions compared to theoriginal radius curvature. As the faceplate becomes more flat, theradius of curvature increases. The club head assembly having a faceplate14 with untreated Ti-7S⁺ flattened significantly in both its roll andbulge dimensions within 50 hits on a golf ball. In contrast, the clubhead assembly having a Ti-7S⁺ faceplate treated at 650° C. maintainedits curvature significantly better than the first club head assemblyafter 2,000 hits. The main changes in roll and bulge dimensions occurwithin the first 50 to 100 hits, as seen in FIG. 16. The Ti-7S⁺faceplate treated at 650° C. maintained its curvature better in bothroll and bulge dimensions after 2,000 hits than the first club headassembly having a faceplate 14 of untreated Ti-7S⁺.

For heat treatments below the solvus temperature (for example, at 400°C.), Ti₃Al particles become more mobile and can precipitate into theα-matrix. Some of the Ti₃Al particles gather at grain boundaries and ageharden the material. In contrast, for heat treatments above the solvustemperature (for example, at 650° C. or 700° C.), Ti₃Al particlesinstead dissolve within the α-matrix. The brittle Ti₃Al particles canact as points of stress. Dissolving brittle Ti₃Al particles within theα-matrix thereby acts as a stress relief. This “stress relief” processenables the club head assembly 30 to better withstand tensile andcompressive forces during impact against a golf ball.

In one embodiment, the faceplate 14 that is formed from Ti-7S⁺ and heattreated above the solvus temperature of Ti-7S⁺ remains within ˜7%deflection of its original roll curvature and within ˜4% of its originalbulge after about 25 strikes. In one embodiment, the faceplate 14 thatis formed from untreated Ti-7S⁺ remains within ˜11% deflection of itsoriginal roll curvature and within ˜8% deflection of its original bulgecurvature after about 25 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S⁺ and heattreated above the solvus temperature of Ti-7S⁺ remains within ˜4%deflection of its original roll curvature and within ˜2% of its originalbulge after about 50 strikes. In one embodiment, the faceplate 14 thatis formed from untreated Ti-7S⁺ remains within ˜15% deflection of itsoriginal roll curvature and within ˜12% deflection of its original bulgecurvature after about 50 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S⁺ and heattreated above the solvus temperature of Ti-7S⁺ remains within ˜6%deflection of its original roll curvature and within ˜3% of its originalbulge after about 100 strikes. In one embodiment, the faceplate 14 thatis formed from untreated Ti-7S⁺ remains within ˜15% deflection of itsoriginal roll curvature and within ˜10% deflection of its original bulgecurvature after about 100 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S⁺ and heattreated above the solvus temperature of Ti-7S⁺ remains within ˜5%deflection of its original roll curvature and within ˜3% of its originalbulge after about 175 strikes. In one embodiment, the faceplate 14 thatis formed from untreated Ti-7S⁺ remains within ˜18% deflection of itsoriginal roll curvature and within ˜12% deflection of its original bulgecurvature after about 175 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S⁺ and heattreated above the solvus temperature of Ti-7S⁺ remains within 5% to 10%deflection of its original roll curvature and within 2% to 5% of itsoriginal bulge after any number of strikes between about 175 and 2,000strikes. In one embodiment, the faceplate 14 that is formed fromuntreated Ti-7S⁺ remains within 15% to 20% deflection of its originalroll curvature and within 10% to 15% deflection of its original bulgecurvature after any number of strikes between about 175 and 2,000strikes.

As shown in FIG. 17, an experiment was performed to compare the effectof various heat treatment temperatures on the faceplate 14 over thecourse of 2,000 hits or ball strikes. However, the data presented inFIG. 16 is limited to the first 175 hits or ball strikes wherein themajority of the changes take place. The data between 175 and 2,000 hitsor ball strikes plateaus and follows a similar progression as the datadisplayed for 50 to 175 hits. The faceplates 14 were formed from Ti-7S⁺alloy. One club head assembly was not heat treated. A second club headassembly was heated to 700° C., which is above the solvus temperature ofthe Ti-7S⁺ alloy. The measurement data provided in FIG. 16 represent thepercent change in the radius of curvature of the bulge and the rolldimensions compared to the original radius curvature. As the faceplatebecomes more flat, the radius of curvature increases. The club headassembly having a faceplate 14 with untreated Ti-7S⁺ flattenedsignificantly in both its roll and bulge dimensions within 50 hits on agolf ball. In contrast, the club head assembly having a Ti-7S⁺ faceplatetreated at 650° C. maintained its curvature significantly better thanthe first club head assembly after 2,000 hits. The main changes in rolland bulge dimensions occur within the first 50 to 100 hits, as seen inFIG. 16. The Ti-7S⁺ faceplate treated at 700° C. maintained itscurvature better in both roll and bulge dimensions after 2,000 hits thanthe first club head assembly having a faceplate 14 of untreated Ti-7S⁺.

In one embodiment, the faceplate 14 that is formed from Ti-7S⁺ and heattreated above the solvus temperature of Ti-7S⁺ remains within ˜8%deflection of its original roll curvature and within ˜6% of its originalbulge after about 25 strikes. In one embodiment, the faceplate 14 thatis formed from untreated Ti-7S⁺ remains within ˜11% deflection of itsoriginal roll curvature and within ˜8% deflection of its original bulgecurvature after about 25 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S⁺ and heattreated above the solvus temperature of Ti-7S⁺ remains within ˜8%deflection of its original roll curvature and within ˜4% of its originalbulge after about 50 strikes. In one embodiment, the faceplate 14 thatis formed from untreated Ti-7S⁺ remains within ˜15% deflection of itsoriginal roll curvature and within ˜12% deflection of its original bulgecurvature after about 50 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S⁺ and heattreated above the solvus temperature of Ti-7S⁺ remains within ˜9%deflection of its original roll curvature and within ˜4% of its originalbulge after about 100 strikes. In one embodiment, the faceplate 14 thatis formed from untreated Ti-7S⁺ remains within ˜15% deflection of itsoriginal roll curvature and within ˜10% deflection of its original bulgecurvature after about 100 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S⁺ and heattreated above the solvus temperature of Ti-7S⁺ remains within ˜9%deflection of its original roll curvature and within ˜3% of its originalbulge after about 175 strikes. In one embodiment, the faceplate 14 thatis formed from untreated Ti-7S⁺ remains within ˜18% deflection of itsoriginal roll curvature and within ˜12% deflection of its original bulgecurvature after about 175 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S⁺ and heattreated above the solvus temperature of Ti-7S⁺ remains within 5% to 10%deflection of its original roll curvature and within 2% to 6% of itsoriginal bulge after any number of strikes between about 175 and 2,000strikes. In one embodiment, the faceplate 14 that is formed fromuntreated Ti-7S⁺ remains within 15% to 20% deflection of its originalroll curvature and within 10% to 15% deflection of its original bulgecurvature after any number of strikes between about 175 and 2,000strikes.

The measurement data provided in Table 1, shown below, represents thepercent changes in the radius of curvature of the bulge and rolldimensions compared to the original radius of curvature for theembodiments tracked in FIGS. 16 and 17.

TABLE 1 Raw data for the percentage deflection of the roll and bulge onTi-7S⁺ alloys with and without heat treatment at various temperatures.Ti-7S⁺ Ti-7S⁺ Ti-7S⁺ Ti-7S⁺ Ti-7S⁺ Ti-7S⁺ No HT No HT 650° C. 650° C.700° C. 700° C. Hits Roll Bulge Roll Bulge Roll Bulge 0 0% 0% 0% 0% 0%0% 25 11% 8% 7% 4% 8% 6% 50 15% 12% 4% 2% 8% 4% 100 15% 10% 6% 3% 9% 4%175 18% 12% 5% 3% 9% 3%

Furthermore, an experiment was performed to compare the effect ofvarious heat treatment temperatures on the faceplate 14 over the courseof 2,000 hits or ball strikes. The faceplate 14 was formed from α-β Tialloy. One club head assembly was heated to 400° C., which is below thesolvus temperature of the α-β Ti alloy. A second club head assembly washeated to 600° C., which is above the solvus temperature of the α-β Tialloy. The club head assembly treated at 400° C. flattened significantlyin both its roll and bulge dimensions within 25 hits on a golf ball. Incontrast, the club head assembly treated at 600° C. did not begin toflatten until 225 strikes on a golf ball and maintained its curvaturesignificantly better than the first club head assembly after 2,000 hits.

In one embodiment, the club head assembly treated at 500° C. maintainedits original bulge and roll curvature after 25 hits. In one embodiment,the club head assembly treated at 500° C. maintained its original bulgeand roll curvature after 50 hits. In one embodiment, the club headassembly treated at 500° C. maintained its original bulge and rollcurvature after 75 hits. In one embodiment, the club head assemblytreated at 500° C. maintained its original bulge and roll curvatureafter 100 hits. In one embodiment, the club head assembly treated at500° C. maintained its original bulge and roll curvature after 125 hits.In one embodiment, the club head assembly treated at 500° C. maintainedits original bulge and roll curvature after 150 hits. In one embodiment,the club head assembly treated at 500° C. maintained its original bulgeand roll curvature after 175 hits. In one embodiment, the club headassembly treated at 500° C. maintained its original bulge and rollcurvature after 200 hits. In one embodiment, the club head assemblytreated at 500° C. maintained its original bulge and roll curvatureafter 225 hits.

In one embodiment, the club head assembly treated at 500° C.substantially maintained its bulge and roll curvature after 250 hits. Inone embodiment, the club head assembly treated at 500° C. substantiallymaintained its bulge and roll curvature after 275 hits. In oneembodiment, the club head assembly treated at 500° C. substantiallymaintained its bulge and roll curvature after 300 hits. In oneembodiment, the club head assembly treated at 500° C. substantiallymaintained its bulge and roll curvature after 500 hits. In oneembodiment, the club head assembly treated at 500° C. substantiallymaintained its bulge and roll curvature after 1,000 hits. In oneembodiment, the club head assembly treated at 500° C. substantiallymaintained its bulge and roll curvature after 1500 hits. In oneembodiment, the club head assembly treated at 500° C. substantiallymaintained its bulge and roll curvature after 2,000 hits.

In one embodiment, the club head assembly treated at 600° C. maintainedits original bulge and roll curvature after 25 hits. In one embodiment,the club head assembly treated at 600° C. maintained its original bulgeand roll curvature after 50 hits. In one embodiment, the club headassembly treated at 600° C. maintained its original bulge and rollcurvature after 75 hits. In one embodiment, the club head assemblytreated at 600° C. maintained its original bulge and roll curvatureafter 100 hits. In one embodiment, the club head assembly treated at600° C. maintained its original bulge and roll curvature after 125 hits.In one embodiment, the club head assembly treated at 600° C. maintainedits original bulge and roll curvature after 150 hits. In one embodiment,the club head assembly treated at 600° C. maintained its original bulgeand roll curvature after 175 hits. In one embodiment, the club headassembly treated at 600° C. maintained its original bulge and rollcurvature after 200 hits. In one embodiment, the club head assemblytreated at 600° C. maintained its original bulge and roll curvatureafter 225 hits.

In one embodiment, the club head assembly treated at 600° C.substantially maintained its bulge and roll curvature after 250 hits. Inone embodiment, the club head assembly treated at 600° C. substantiallymaintained its bulge and roll curvature after 275 hits. In oneembodiment, the club head assembly treated at 600° C. substantiallymaintained its bulge and roll curvature after 300 hits. In oneembodiment, the club head assembly treated at 600° C. substantiallymaintained its bulge and roll curvature after 500 hits. In oneembodiment, the club head assembly treated at 600° C. substantiallymaintained its bulge and roll curvature after 1,000 hits. In oneembodiment, the club head assembly treated at 600° C. substantiallymaintained its bulge and roll curvature after 1500 hits. In oneembodiment, the club head assembly treated at 600° C. substantiallymaintained its bulge and roll curvature after 2,000 hits.

In one embodiment, the club head assembly treated at 600° C. maintainedits original bulge curvature and its roll curvature radius increasedfrom 11 inches to 13 inches after 250 hits. In one embodiment, the clubhead assembly treated at 600° C. maintained its original bulge curvatureand maintained a roll curvature radius of 13 inches after 275 hits. Inone embodiment, the club head assembly treated at 600° C. increased itsbulge curvature radius from 12 inches to 13 inches and maintained a rollcurvature radius of 13 inches after 300 hits. In one embodiment, theclub head assembly treated at 600° C. maintained its bulge curvatureradius of 13 inches and maintained a roll curvature radius of 13 inchesafter 500 hits. In one embodiment, the club head assembly treated at600° C. maintained its bulge curvature radius of 13 inches and increasedits roll curvature radius from 13 inches to 14 inches after 1,000 hits.In one embodiment, the club head assembly treated at 600° C. maintainedits bulge curvature radius of 13 inches and maintained a roll curvatureradius of 14 inches after 1,500 hits. In one embodiment, the club headassembly treated at 600° C. maintained its bulge curvature radius of 13inches and maintained a roll curvature radius of 14 inches after 2,000hits.

In one embodiment, the club head assembly treated at 700° C. maintainedits original bulge and roll curvature after 25 hits. In one embodiment,the club head assembly treated at 700° C. maintained its original bulgeand roll curvature after 50 hits. In one embodiment, the club headassembly treated at 700° C. maintained its original bulge and rollcurvature after 75 hits. In one embodiment, the club head assemblytreated at 700° C. maintained its original bulge and roll curvatureafter 100 hits. In one embodiment, the club head assembly treated at700° C. maintained its original bulge and roll curvature after 125 hits.In one embodiment, the club head assembly treated at 700° C. maintainedits original bulge and roll curvature after 150 hits. In one embodiment,the club head assembly treated at 700° C. maintained its original bulgeand roll curvature after 175 hits. In one embodiment, the club headassembly treated at 700° C. maintained its original bulge and rollcurvature after 200 hits. In one embodiment, the club head assemblytreated at 700° C. maintained its original bulge and roll curvatureafter 225 hits.

In one embodiment, the club head assembly treated at 700° C.substantially maintained its bulge and roll curvature after 250 hits. Inone embodiment, the club head assembly treated at 700° C. substantiallymaintained its bulge and roll curvature after 275 hits. In oneembodiment, the club head assembly treated at 700° C. substantiallymaintained its bulge and roll curvature after 300 hits. In oneembodiment, the club head assembly treated at 700° C. substantiallymaintained its bulge and roll curvature after 500 hits. In oneembodiment, the club head assembly treated at 700° C. substantiallymaintained its bulge and roll curvature after 1,000 hits. In oneembodiment, the club head assembly treated at 700° C. substantiallymaintained its bulge and roll curvature after 1500 hits. In oneembodiment, the club head assembly treated at 700° C. substantiallymaintained its bulge and roll curvature after 2,000 hits.

In one embodiment, the club head assembly treated at 800° C. maintainedits original bulge and roll curvature after 25 hits. In one embodiment,the club head assembly treated at 800° C. maintained its original bulgeand roll curvature after 50 hits. In one embodiment, the club headassembly treated at 800° C. maintained its original bulge and rollcurvature after 75 hits. In one embodiment, the club head assemblytreated at 800° C. maintained its original bulge and roll curvatureafter 100 hits. In one embodiment, the club head assembly treated at800° C. maintained its original bulge and roll curvature after 125 hits.In one embodiment, the club head assembly treated at 800° C. maintainedits original bulge and roll curvature after 150 hits. In one embodiment,the club head assembly treated at 800° C. maintained its original bulgeand roll curvature after 175 hits. In one embodiment, the club headassembly treated at 800° C. maintained its original bulge and rollcurvature after 200 hits. In one embodiment, the club head assemblytreated at 800° C. maintained its original bulge and roll curvatureafter 225 hits.

In one embodiment, the club head assembly treated at 800° C.substantially maintained its bulge and roll curvature after 250 hits. Inone embodiment, the club head assembly treated at 800° C. substantiallymaintained its bulge and roll curvature after 275 hits. In oneembodiment, the club head assembly treated at 800° C. substantiallymaintained its bulge and roll curvature after 300 hits. In oneembodiment, the club head assembly treated at 800° C. substantiallymaintained its bulge and roll curvature after 500 hits. In oneembodiment, the club head assembly treated at 800° C. substantiallymaintained its bulge and roll curvature after 1,000 hits. In oneembodiment, the club head assembly treated at 800° C. substantiallymaintained its bulge and roll curvature after 1500 hits. In oneembodiment, the club head assembly treated at 800° C. substantiallymaintained its bulge and roll curvature after 2,000 hits.

In one embodiment, the club head assembly treated at 900° C. maintainedits original bulge and roll curvature after 25 hits. In one embodiment,the club head assembly treated at 900° C. maintained its original bulgeand roll curvature after 50 hits. In one embodiment, the club headassembly treated at 900° C. maintained its original bulge and rollcurvature after 75 hits. In one embodiment, the club head assemblytreated at 900° C. maintained its original bulge and roll curvatureafter 100 hits. In one embodiment, the club head assembly treated at900° C. maintained its original bulge and roll curvature after 125 hits.In one embodiment, the club head assembly treated at 900° C. maintainedits original bulge and roll curvature after 150 hits. In one embodiment,the club head assembly treated at 900° C. maintained its original bulgeand roll curvature after 175 hits. In one embodiment, the club headassembly treated at 900° C. maintained its original bulge and rollcurvature after 200 hits. In one embodiment, the club head assemblytreated at 900° C. maintained its original bulge and roll curvatureafter 225 hits.

In one embodiment, the club head assembly treated at 900° C.substantially maintained its bulge and roll curvature after 250 hits. Inone embodiment, the club head assembly treated at 900° C. substantiallymaintained its bulge and roll curvature after 275 hits. In oneembodiment, the club head assembly treated at 900° C. substantiallymaintained its bulge and roll curvature after 300 hits. In oneembodiment, the club head assembly treated at 900° C. substantiallymaintained its bulge and roll curvature after 500 hits. In oneembodiment, the club head assembly treated at 900° C. substantiallymaintained its bulge and roll curvature after 1,000 hits. In oneembodiment, the club head assembly treated at 900° C. substantiallymaintained its bulge and roll curvature after 1500 hits. In oneembodiment, the club head assembly treated at 900° C. substantiallymaintained its bulge and roll curvature after 2,000 hits.

In one embodiment, the club head assembly treated at 1000° C. maintainedits original bulge and roll curvature after 25 hits. In one embodiment,the club head assembly treated at 1000° C. maintained its original bulgeand roll curvature after 50 hits. In one embodiment, the club headassembly treated at 1000° C. maintained its original bulge and rollcurvature after 75 hits. In one embodiment, the club head assemblytreated at 1000° C. maintained its original bulge and roll curvatureafter 100 hits. In one embodiment, the club head assembly treated at1000° C. maintained its original bulge and roll curvature after 125hits. In one embodiment, the club head assembly treated at 1000° C.maintained its original bulge and roll curvature after 150 hits. In oneembodiment, the club head assembly treated at 1000° C. maintained itsoriginal bulge and roll curvature after 175 hits. In one embodiment, theclub head assembly treated at 1000° C. maintained its original bulge androll curvature after 200 hits. In one embodiment, the club head assemblytreated at 1000° C. maintained its original bulge and roll curvatureafter 225 hits.

In one embodiment, the club head assembly treated at 1000° C.substantially maintained its bulge and roll curvature after 250 hits. Inone embodiment, the club head assembly treated at 1000° C. substantiallymaintained its bulge and roll curvature after 275 hits. In oneembodiment, the club head assembly treated at 1000° C. substantiallymaintained its bulge and roll curvature after 300 hits. In oneembodiment, the club head assembly treated at 1000° C. substantiallymaintained its bulge and roll curvature after 500 hits. In oneembodiment, the club head assembly treated at 1000° C. substantiallymaintained its bulge and roll curvature after 1,000 hits. In oneembodiment, the club head assembly treated at 1000° C. substantiallymaintained its bulge and roll curvature after 1500 hits. In oneembodiment, the club head assembly treated at 1000° C. substantiallymaintained its bulge and roll curvature after 2,000 hits.

In one embodiment, the club head assembly treated at 1100° C. maintainedits original bulge and roll curvature after 25 hits. In one embodiment,the club head assembly treated at 1100° C. maintained its original bulgeand roll curvature after 50 hits. In one embodiment, the club headassembly treated at 1100° C. maintained its original bulge and rollcurvature after 75 hits. In one embodiment, the club head assemblytreated at 1100° C. maintained its original bulge and roll curvatureafter 100 hits. In one embodiment, the club head assembly treated at1100° C. maintained its original bulge and roll curvature after 125hits. In one embodiment, the club head assembly treated at 1100° C.maintained its original bulge and roll curvature after 150 hits. In oneembodiment, the club head assembly treated at 1100° C. maintained itsoriginal bulge and roll curvature after 175 hits. In one embodiment, theclub head assembly treated at 1100° C. maintained its original bulge androll curvature after 200 hits. In one embodiment, the club head assemblytreated at 1100° C. maintained its original bulge and roll curvatureafter 225 hits.

In one embodiment, the club head assembly treated at 1100° C.substantially maintained its bulge and roll curvature after 250 hits. Inone embodiment, the club head assembly treated at 1100° C. substantiallymaintained its bulge and roll curvature after 275 hits. In oneembodiment, the club head assembly treated at 1100° C. substantiallymaintained its bulge and roll curvature after 300 hits. In oneembodiment, the club head assembly treated at 1100° C. substantiallymaintained its bulge and roll curvature after 500 hits. In oneembodiment, the club head assembly treated at 1100° C. substantiallymaintained its bulge and roll curvature after 1,000 hits. In oneembodiment, the club head assembly treated at 1100° C. substantiallymaintained its bulge and roll curvature after 1500 hits. In oneembodiment, the club head assembly treated at 1100° C. substantiallymaintained its bulge and roll curvature after 2,000 hits.

In one embodiment, the club head assembly treated at 1200° C. maintainedits original bulge and roll curvature after 25 hits. In one embodiment,the club head assembly treated at 1200° C. maintained its original bulgeand roll curvature after 50 hits. In one embodiment, the club headassembly treated at 1200° C. maintained its original bulge and rollcurvature after 75 hits. In one embodiment, the club head assemblytreated at 1200° C. maintained its original bulge and roll curvatureafter 100 hits. In one embodiment, the club head assembly treated at1200° C. maintained its original bulge and roll curvature after 125hits. In one embodiment, the club head assembly treated at 1200° C.maintained its original bulge and roll curvature after 150 hits. In oneembodiment, the club head assembly treated at 1200° C. maintained itsoriginal bulge and roll curvature after 175 hits. In one embodiment, theclub head assembly treated at 1200° C. maintained its original bulge androll curvature after 200 hits. In one embodiment, the club head assemblytreated at 1200° C. maintained its original bulge and roll curvatureafter 225 hits.

In one embodiment, the club head assembly treated at 1200° C.substantially maintained its bulge and roll curvature after 250 hits. Inone embodiment, the club head assembly treated at 1200° C. substantiallymaintained its bulge and roll curvature after 275 hits. In oneembodiment, the club head assembly treated at 1200° C. substantiallymaintained its bulge and roll curvature after 300 hits. In oneembodiment, the club head assembly treated at 1200° C. substantiallymaintained its bulge and roll curvature after 500 hits. In oneembodiment, the club head assembly treated at 1200° C. substantiallymaintained its bulge and roll curvature after 1,000 hits. In oneembodiment, the club head assembly treated at 1200° C. substantiallymaintained its bulge and roll curvature after 1500 hits. In oneembodiment, the club head assembly treated at 1200° C. substantiallymaintained its bulge and roll curvature after 2,000 hits.

In one embodiment, the club head assembly treated at or above the solvustemperature maintained its original bulge and roll curvature after 25hits. In one embodiment, the club head assembly treated at or above thesolvus temperature maintained its original bulge and roll curvatureafter 50 hits. In one embodiment, the club head assembly treated at orabove the solvus temperature maintained its original bulge and rollcurvature after 75 hits. In one embodiment, the club head assemblytreated at or above the solvus temperature maintained its original bulgeand roll curvature after 100 hits. In one embodiment, the club headassembly treated at or above the solvus temperature maintained itsoriginal bulge and roll curvature after 125 hits. In one embodiment, theclub head assembly treated at or above the solvus temperature maintainedits original bulge and roll curvature after 150 hits. In one embodiment,the club head assembly treated at or above the solvus temperaturemaintained its original bulge and roll curvature after 175 hits. In oneembodiment, the club head assembly treated at or above the solvustemperature maintained its original bulge and roll curvature after 200hits. In one embodiment, the club head assembly treated at or above thesolvus temperature maintained its original bulge and roll curvatureafter 225 hits.

In one embodiment, the club head assembly treated at or above the solvustemperature substantially maintained its bulge and roll curvature after250 hits. In one embodiment, the club head assembly treated at or abovethe solvus temperature substantially maintained its bulge and rollcurvature after 275 hits. In one embodiment, the club head assemblytreated at or above the solvus temperature substantially maintained itsbulge and roll curvature after 300 hits. In one embodiment, the clubhead assembly treated at or above the solvus temperature substantiallymaintained its bulge and roll curvature after 500 hits. In oneembodiment, the club head assembly treated at or above the solvustemperature substantially maintained its bulge and roll curvature after1,000 hits. In one embodiment, the club head assembly treated at orabove the solvus temperature substantially maintained its bulge and rollcurvature after 1500 hits. In one embodiment, the club head assemblytreated at or above the solvus temperature substantially maintained itsbulge and roll curvature after 2,000 hits.

Also, as shown in FIG. 8, a follow-up experiment was performed tocompare the impact of a 600° C. heat treatment on three differentfaceplate geometries. The roll measurements for all three faceplategeometries were consistent, confirming that the stress-relief heattreatment increases the faceplate's ability to maintain its curvature.The faceplate comprised the Ti-9S (or T-9S) alloy.

Referring now to FIG. 9, an experiment was performed to compare theeffect of various heat treatment temperatures on the faceplate 14 overthe course of 2,000 hits or ball strikes. The faceplates 14 were formedfrom Ti-9S (or T-9S) alloy. One club head assembly was heated to 550°C., which is below the solvus temperature of the Ti-9S (or T-9S) alloy.A second club head assembly was heated to 575° C. and a third club headwas heated to 600° C., which is above the solvus temperature of theTi-9S (or T-9S) alloy. The measurement data provided in FIG. 9 representthe percentage change in the radius of curvature of the bulge and theroll dimensions compared to the original radius curvature. As thefaceplate becomes more flat, the radius of curvature increases. The clubhead assembly treated at 550° C. flattened significantly in both itsroll and bulge dimensions within a few hits on a golf ball. In contrast,the club head assembly treated at 600° C. maintained its curvaturesignificantly better than the club head assemblies after 2,000 hits.

In one embodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 600° C. remains within 1% deflection of its original rollcurvature and within 3% deflection of its original bulge curvature after25 strikes. In one embodiment, the faceplate 14 formed from Ti-9S (orT-9S) and heat treated at 575° C. remains within 24% deflection of itsoriginal roll curvature and within 11% deflection of its original bulgecurvature after 25 strikes. In one embodiment, the faceplate 14 formedfrom Ti-9S (or T-9S) and heat treated at 550° C. remains within 19%deflection of its original roll curvature and within 9% deflection ofits original bulge curvature after 25 strikes.

In one embodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 600° C. retains its original roll curvature and is within 4%deflection of its original bulge curvature after 50 strikes. In oneembodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 575° C. remains within 28% deflection of its original rollcurvature and within 13% deflection of its original bulge curvatureafter 50 strikes. In one embodiment, the faceplate 14 formed from Ti-9S(or T-9S) and heat treated at 550° C. remains within 23% deflection ofits original roll curvature and within 15% deflection of its originalbulge curvature after 50 strikes.

In one embodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 600° C. retains its original roll curvature and is within 5%deflection of its original bulge curvature after 75 strikes. In oneembodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 575° C. remains within 28% deflection of its original rollcurvature and within 12% deflection of its original bulge curvatureafter 75 strikes. In one embodiment, the faceplate 14 formed from Ti-9S(or T-9S) and heat treated at 550° C. remains within 28% deflection ofits original roll curvature and within 23% deflection of its originalbulge curvature after 75 strikes.

In one embodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 600° C. retains its original roll curvature and is within 6%deflection of its original bulge curvature after 100 strikes. In oneembodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 575° C. remains within 30% deflection of its original rollcurvature and within 13% deflection of its original bulge curvatureafter 100 strikes. In one embodiment, the faceplate 14 formed from Ti-9S(or T-9S) and heat treated at 550° C. remains within 29% deflection ofits original roll curvature and within 22% deflection of its originalbulge curvature after 100 strikes.

In one embodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 600° C. retains its original roll curvature and is within 7%deflection of its original bulge curvature after 150 strikes. In oneembodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 575° C. remains within 28% deflection of its original rollcurvature and within 13% deflection of its original bulge curvatureafter 150 strikes. In one embodiment, the faceplate 14 formed from Ti-9S(or T-9S) and heat treated at 550° C. remains within 31% deflection ofits original roll curvature and within 24% deflection of its originalbulge curvature after 150 strikes.

In one embodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 600° C. remains within 5% deflection of its original rollcurvature and within 5% deflection of its original bulge curvature after300 strikes. In one embodiment, the faceplate 14 formed from Ti-9S (orT-9S) and heat treated at 575° C. remains within 28% deflection of itsoriginal roll curvature and within 14% deflection of its original bulgecurvature after 300 strikes. In one embodiment, the faceplate 14 formedfrom Ti-9S (or T-9S) and heat treated at 550° C. remains within 34%deflection of its original roll curvature and within 26% deflection ofits original bulge curvature after 300 strikes.

In one embodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 600° C. remains within 4% deflection of its original rollcurvature and within 7% deflection of its original bulge curvature after1,000 strikes. In one embodiment, the faceplate 14 formed from Ti-9S (orT-9S) and heat treated at 575° C. remains within 27% deflection of itsoriginal roll curvature and within 13% deflection of its original bulgecurvature after 1,000 strikes. In one embodiment, the faceplate 14formed from Ti-9S (or T-9S) and heat treated at 550° C. remains within34% deflection of its original roll curvature and within 27% deflectionof its original bulge curvature after 1,000 strikes.

In one embodiment, the faceplate 14 formed from Ti-9S (or T-9S) and heattreated at 600° C. remains within 5% deflection of its original rollcurvature and within 6% deflection of its original bulge curvature after2,000 strikes. In one embodiment, the faceplate 14 formed from Ti-9S (orT-9S) and heat treated at 575° C. remains within 25% deflection of itsoriginal roll curvature and within 15% deflection of its original bulgecurvature after 2,000 strikes. In one embodiment, the faceplate 14formed from Ti-9S (or T-9S) and heat treated at 550° C. remains within34% deflection of its original roll curvature and within 28% deflectionof its original bulge curvature after 2,000 strikes.

As shown in FIG. 10, an experiment was performed to compare thedurability of faceplate 14 when composed of either the Ti-6-4 alloy orthe Ti-9S (T-9S) alloy. The experiment tracked the number of strikesfrom an air cannon until failure of the faceplate 14. One club headassembly used Ti 6-4 alloy as the faceplate material. A second club headassembly used a different model club head with Ti 6-4 alloy as thefaceplate material (data not shown). A third club head assembly used athird model club head with the Ti 6-4 alloy as the faceplate material(data not shown). A fourth club head assembly uses the same model clubhead as the third club head assembly, with Ti-9S (or T-9S) alloy as thefaceplate material. The measurement data provided in FIG. 10 representsthe number of hits until failure of the faceplate. The club headassembly with the T-9S (or Ti-9S) alloy faceplate showed increaseddurability over assemblies with Ti 6-4 alloy faceplates. The same clubhead model showed an increased durability of about 3200 hits untilfailure of the faceplate with T-9S (or Ti-9S) alloy as the faceplatematerial, as opposed to a durability of 2600 hits until failure with Ti6-4 alloy as the faceplate material.

Table 2, shown below, quantifies the composition of Ti-6Al-4V (or Ti6-4), Ti-7S⁺ (or Ti-7S, T-7S, or ST721), Ti-9S (or T-9S), and Ti-8-1-1alloys. Table 3, shown below, is a chart showing the mechanicalproperties of various α-β Ti alloys. This data is based on METL reportsand verified with industry standards and supplier data sheets. Table 4is a chart showing the projected weight savings based on one embodiment.Due to the strength of the Ti-7S⁺ alloy, a Ti-7S⁺ face may have athickness of approximately 10% thinner or approximately 15% thinner thanthe Ti 6-4 alloy. This reduced thickness of the face can result insignificant weight savings.

TABLE 2 Chart showing the compositions of Ti-7S⁺, T-9S, Ti 6-4, andTi-8-1-1. C Si Mo Fe Al V Sn O N Ti 7s+ 0.05 0.25 2-3 0.5-1.5 7-80.5-1.5 trace 0.20 0.04 balance max max max max 9s 0.08 0.20 trace 0.306.50-8.50 1.00-2.00 trace 0.20 trace balance max max max 8.50 2.00 max6-4 0.08 0.03 trace 0.30 5.50-6.75 3.50-4.50 0.015 0.20 trace balancemax max max max max 8-1-1 0.08 trace 0.75-1.25 0.30 7.50-8.50 0.75-1.250.015 0.12 trace balance max max max max

TABLE 3 Chart showing the mechanical properties of various α-β Tialloys. 17-4 T9S Sheet* T9S Sheet* Ti-7S⁺ Ti 6-4 Ti 6-4 Ti 8-1-1 Ti8-1-1 Sheet (transverse) (longitudinal) Sheet Cast Sheet Cast Sheet CondA Yield (ksi) 135-145 135-145 165-185 115-125 125-135 110-120 115-125130-140 Tensile 145-155 155-165 185-195 125-135 130-140 125-135 125-135150-160 (ksi) Elongation  7-12 14-19 8.5% 13-18 12-15  7-12  8-10 4-6(%) Young's 15.9 15.2 13.9 16.2 16.5 18.0 17.5 28.5 Modulus (Mpsi)*Samples had driver heat treat (600° C. for 1 hour)

TABLE 4 Chart showing the projected weight savings based on selectedembodiments. Wt Outer Center Savings Face Face Face Face Over Body BodyThickness Thickness Density Volume Mass Ti 6-4 Volume Mass (inches)(inches) (lb/in³) (g/in³) (in³) (grams) (grams) (in³) (grams) Ti 6-40.090 0.140 0.1597 72.44 0.592 42.9 — 1.9013 137.7 (current) Ti 8-1-10.090 0.140 0.1575 71.44 0.592 42.3 0.6 1.9013 135.8 T9S 0.090 0.1400.1560 70.76 0.592 41.9 1.0 1.9013 134.5 T9S @ 0.086 0.136 0.1560 70.760.563 39.8 3.1 1.9013 134.5 5% thinner T9S @ 0.081 0.131 0.1560 70.760.533 37.7 5.2 1.9013 134.5 10% thinner Ti-7S⁺ 0.090 0.140 0.1614 73.250.592 43.4 −0.5 1.9013 139.3 Ti-7S⁺ @ 0.081 0.131 0.1614 73.25 0.53339.0 3.9 1.9013 139.3 10% Thinner Ti-7S⁺ @ 0.076 0.126 0.1614 73.250.502 36.8 6.1 1.9013 139.3 15% Thinner

FIG. 11A shows the grains in the microstructure of an α-β Ti alloy thathas not been through heat treat. Distinct striations of (3 bands can beseen among pockets of the α/β matrix. In contrast, FIG. 11B shows thegrains in the microstructure of an α-β Ti alloy that has been throughheat treat. Here, the grains show directionality in the crown-to-soledirection. The corresponding stress-strain curves of the no heat treatand heat treated samples, FIGS. 12C and 12D, show the benefits of heattreat. The stress/strain curve of the non-heat treated α-β Ti alloy(FIG. 11C) shows unstable yielding at high strain rates, most likely dueto deformation of β bands. The β bands are known to have a differentplasticity value compared to the α/β matrix, which causes theaforementioned deformation at high strain rates. The stress/strain curveof the heat treated α-β Ti alloy (FIG. 11D) is more stable and atteststo stresses transferring more easily along grain boundaries at highstrain rates.

FIG. 12 shows the phase diagram of Ti and Al alloys. The α+Ti₃Al shadedregion represents α-β Ti alloys which have not yet undergone heattreatment. α+Ti₃Al is brittle material unsuitable for faceplatemanufacturing. When α+Ti₃Al is heated above its solvus temperature,indicated via the vertical line, it changes to αTi phase. During thistransition, the Ti₃Al in the α+Ti₃Al goes into solution and relieves thebrittle properties of α+Ti₃Al. As shown in the diagram, the temperaturechange for this transition depends on the percent of aluminum in theα+Ti₃Al.

FIG. 14 shows a phase diagram including lines representing Ti-7S⁺ andT9S materials. As illustrated, the solvus temperature for T9S is around580° C. which is lower than the solvus temperature for Ti-7S⁺, which isaround 630° C. Although the percent weight of aluminum is only slightlyhigher in Ti-7S⁺ than in T9S, the high solvus temperature of Ti-7S⁺requires that it be treated at a much higher temperature (betweenapproximately 650° C. and 700° C., or above 700° C. in some embodiments)than T9S, which can be treated between approximately 600° C. and 650° C.in some embodiments.

As shown in FIG. 13, an experiment was performed to compare the amountof deflection of various faceplates 14 over the course of 0, 25, 50,100, 150, 1000, and 2,000 hits or ball strikes. The faceplates 14 wereformed from Ti 6-4 or Ti-9S (T-9S) alloy. One club head assembly made ofTi 6-4 alloy was not heat treated. A second club head assembly made ofTi6-4 alloy was heated to 600° C., which is above the solvus temperatureof the Ti-9S (or T-9S) alloy. A third club head assembly made of the theTi-9S (or T-9S) alloy was heated to 600° C., which is above the solvustemperature of the Ti-9S (or T-9S) alloy. The measurement data providedin Table 5, shown below, represent the percent change in the radius ofcurvature of the bulge and the roll dimensions compared to the originalradius curvature.

TABLE 5 Raw data for the percentage deflection of the roll and bulge onTi 6-4 alloys with and without heat treat and T-9S alloys with heattreat. Ti 6- Ti 6-4 Ti 6-4 Ti 6-4 T9S T9S 4 No No HT 600° C. 600° C.600° C. 600° C. Hits HT Roll Bulge Roll Bulge Roll Bulge 0 0% 0% 0% 0%0% 0% 25 2% 7% 10% 4% 0% 1% 50 4% 8% 12% 6% 8% 7% 100 13% 9% 16% 7% 8%8% 150 13% 10% 19% 11% 8% 8% 1000 21% 16% 25% 15% 9% 8% 2000 22% 17% 30%15% 10% 10%

As the faceplate becomes more flat, the radius of curvature increases.The club head assembly having a faceplate 14 made of Ti 6-4 treated at600° C. flattened significantly in both its roll and bulge dimensionsand did not perform like the club head assembly having a faceplate 14made of T9S treated at 600° C. which stayed below 10% deflection in bothits roll and bulge dimensions for all number of hits up to 2,000. Thismay be due to Ti 6-4 having a different or lower wt % Al content; T9Shas 6.5 wt %-8.5 wt % Al and Ti 6-4 has 5.5 wt %-6.75 wt % Al. Thesolvus temperature for Ti 6-4 is lower at ˜540-560° C. compared to thesolvus temperature for T9S, which is ˜560-590° C. Therefore, the 600° C.heat treat did not have the same effect on Ti 6-4 as it did on T9S. TheTi-9S faceplate treated at 600° C. maintained its' curvature betterafter 2000 hits than the club head assemblies having faceplates 14 ofTi-6-4 untreated and heat treated maintained curvature in both roll andbulge dimensions.

As shown in FIG. 15, an experiment was performed to compare the %deflection on the faceplate 14 over the course of 100 and 1000 hits orball strikes. The faceplates 14 were formed from Ti 6-4 or Ti-9S (T-9S)alloy. The various club head assemblies were treated for either 1 or 4hours at 400° C., 550° C., 575° C., 580° C., 600° C., and 700° C. Oneclub head assembly made of Ti 6-4 alloy was not heat treated. A secondclub head assembly made of Ti-9S (or T-9S) alloy was not heat treated. Athird club head assembly made of Ti-9S (or T-9S) alloy was heated for 1hour to 400° C., which is below the solvus temperature of the Ti-9S (orT-9S) alloy. A fourth club head assembly made of Ti-9S (or T-9S) alloywas heated for 1 hour to 550° C., which is below the solvus temperatureof the Ti-9S (or T-9S) alloy. A fifth club head assembly made of Ti-9S(or T-9S) alloy was heated for 1 hour to 575° C., which is below thesolvus temperature of the Ti-9S (or T-9S) alloy. A sixth club headassembly made of Ti-9S (or T-9S) alloy was heated for 4 hours to 580°C., which is the solvus temperature of the Ti-9S (or T-9S) alloy. Aseventh club head assembly made of Ti-9S (or T-9S) alloy was heated for1 hour to 600° C., which is above the solvus temperature of the Ti-9S(or T-9S) alloy. A eighth club head assembly made of Ti-9S (or T-9S)alloy was heated for 4 hours to 600° C., which is above the solvustemperature of the Ti-9S (or T-9S) alloy. A ninth club head assemblymade of Ti-9S (or T-9S) alloy was heated for 1 hour to 700° C., which isabove the solvus temperature of the Ti-9S (or T-9S) alloy. A tenth clubhead assembly made of Ti-9S (or T-9S) alloy was heated for 4 hours to700° C., which is above the solvus temperature of the Ti-9S (or T-9S)alloy. The measurement data provided in FIG. 15 represent the percentchange in the radius of curvature of the bulge and the roll dimensionscompared to the original radius curvature. As the faceplate becomes moreflat, the radius of curvature increases. There is less deflection inroll and much more in bulge going from 575° C. to 580° C. However, atslightly higher temperature (600° C. and above), the percent deflectionfor both measurements drop significantly and then stays the same at evenhigher temperatures. This represents the inflection point where theTi₃Al particles begin to enter the solution. After reaching the 600° C.for 1 hour threshold, increasing the temperature does not give anysignificant improvements to geometric stability. Increasing the durationfrom 1 to 4 hours did not have a significant improvement on percentdeflection either.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated at the solvus temperature of Ti-9S (or T-9S), 580° C.,for 4 hours, has ˜9% deflection from its original bulge and ˜6%deflection from its original roll curvature after about 100 strikes. Inone embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S) andheat treated at the solvus temperature of Ti-9S (or T-9S), 580° C., for4 hours, has ˜10% deflection from its original bulge and ˜6% deflectionfrom its original roll curvature after about 1000 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S), 600°C., for 1 hour, has ˜5% deflection from its original bulge and ˜3%deflection from its original roll curvature after about 100 strikes. Inone embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S) andheat treated above the solvus temperature of Ti-9S (or T-9S), 600° C.,for 1 hour, has ˜6% deflection from its original bulge and ˜5%deflection from its original roll curvature after about 1000 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S), 600°C., for 4 hours, has ˜5% deflection from its original bulge and ˜2%deflection from its original roll curvature after about 100 strikes. Inone embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S) andheat treated above the solvus temperature of Ti-9S (or T-9S), 600° C.,for 4 hours, has ˜6% deflection from its original bulge and ˜3%deflection from its original roll curvature after about 1000 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S), 700°C., for 1 hour, has ˜4% deflection from its original bulge and ˜3%deflection from its original roll curvature after about 100 strikes. Inone embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S) andheat treated above the solvus temperature of Ti-9S (or T-9S), 700° C.,for 1 hour, has ˜5% deflection from its original bulge and ˜3%deflection from its original roll curvature after about 1000 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated above the solvus temperature of Ti-9S (or T-9S), 700°C., for 4 hours, has ˜3% deflection from its original bulge and ˜5%deflection from its original roll curvature after about 100 strikes.

As shown in FIG. 18, an experiment was performed to compare the %deflection on the faceplate 14 over the course of 100 and 1000 hits orball strikes. The faceplates 14 were formed from Ti 6-4, Ti-9S (T-9S),or Ti-7S⁺ alloy. The various club head assemblies were either not heattreated or were treated for 1 hour at 600° C., 650° C., 700° C., or 800°C. One club head assembly made of Ti 6-4 alloy was not heat treated. Asecond club head assembly made of Ti-9S (or T-9S) alloy was not heattreated. A third club head assembly made of Ti-9S (or T-9S) alloy washeated for 1 hour to 600° C., which is above the solvus temperature ofthe Ti-9S (or T-9S) alloy. A fourth club head assembly made of Ti-7S⁺alloy was not heat treated. A fifth club head assembly made of Ti-7S⁺alloy was heated for 1 hour to 650° C., which is above the solvustemperature of the Ti-7S⁺ alloy. A sixth club head assembly made ofTi-7S⁺ alloy was heated for 1 hour to 700° C., which is above the solvustemperature of the Ti-7S⁺ alloy. A seventh club head assembly made ofTi-7S⁺ alloy was heated for 1 hour to 800° C., which is above the solvustemperature of the Ti-7S⁺ alloy. The measurement data provided in FIG.18 represents the percent change in the radius of curvature of the bulgeand the roll dimensions compared to the original radius curvature. Asthe faceplate becomes more flat, the radius of curvature increases. Theassemblies that were heat treated above the solvus temperature of thealloy show significantly lower deflection over 100 and 1000 hits. Asshown through the Ti-7S⁺ data for not treated, treated at 650° C., 700°C., and 800° C., increasing the treatment temperature after the solvustemperature is already attained offers no improvement in percentdeflection. At the solvus temperature, which acts as an inflectionpoint, the Ti₃Al particles begin to enter the solution. After reachingthe inflection point threshold, increasing the temperature does not giveany significant improvements to geometric stability. Furthermore, FIG.18 demonstrates that increasing the number of hits tenfold does notchange the results significantly for the heat treated alloys. Themajority of the deflection for these heat treated faceplates happensduring the first 100 hits, after which the deflection changes less than5%.

In one embodiment, the faceplate 14 that is formed from Ti-9S (or T-9S)and heat treated at 600° C., above the solvus temperature of Ti-9S (orT-9S), has ˜5% deflection from its original bulge and ˜4% deflectionfrom its original roll curvature after about 100 strikes. In oneembodiment, the faceplate 14 that is formed from Ti-9S (or T-9S) andheat treated at 600° C., above the solvus temperature of Ti-9S (orT-9S), has ˜6% deflection from its original bulge and ˜5% deflectionfrom its original roll curvature after about 1000 strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S+ and heattreated at 650° C., above the solvus temperature of Ti-7S+, has ˜3%deflection from its original bulge and ˜6% deflection from its originalroll curvature after about 100 strikes. In one embodiment, the faceplate14 that is formed from Ti-7S+ and heat treated at 650° C., above thesolvus temperature of Ti-7S+, has ˜4% deflection from its original bulgeand ˜10% deflection from its original roll curvature after about 1000strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S+ and heattreated at 700° C., above the solvus temperature of Ti-7S+, has ˜4%deflection from its original bulge and ˜9% deflection from its originalroll curvature after about 100 strikes. In one embodiment, the faceplate14 that is formed from Ti-7S+ and heat treated at 700° C., above thesolvus temperature of Ti-7S+, has ˜5% deflection from its original bulgeand ˜9% deflection from its original roll curvature after about 1000strikes.

In one embodiment, the faceplate 14 that is formed from Ti-7S+ and heattreated at 800° C., above the solvus temperature of Ti-7S+, has ˜6%deflection from its original bulge and ˜9% deflection from its originalroll curvature after about 100 strikes. In one embodiment, the faceplate14 that is formed from Ti-7S+ and heat treated at 800° C., above thesolvus temperature of Ti-7S+, has ˜9% deflection from its original bulgeand ˜11% deflection from its original roll curvature after about 1000strikes.

In one embodiment, the faceplate 14 that is formed from an α-β Ti alloyand heat treated above its solvus temperature, 500-1200° C., has 30% orless deflection from its original bulge and 30% or less deflection fromits original roll curvature after about 2000 strikes or less.

In one embodiment, the faceplate 14 that is formed from an α-β Ti alloyand heat treated at or above its solvus temperature has 30% or lessdeflection from its original bulge and 30% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 25% or lessdeflection from its original bulge and 25% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 20% or lessdeflection from its original bulge and 20% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 15% or lessdeflection from its original bulge and 15% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 10% or lessdeflection from its original bulge and 10% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 9% or lessdeflection from its original bulge and 9% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 8% or lessdeflection from its original bulge and 8% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 7% or lessdeflection from its original bulge and 7% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 6% or lessdeflection from its original bulge and 6% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 5% or lessdeflection from its original bulge and 5% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 4% or lessdeflection from its original bulge and 4% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 3% or lessdeflection from its original bulge and 3% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 2% or lessdeflection from its original bulge and 2% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 1% or lessdeflection from its original bulge and 1% or less deflection from itsoriginal roll curvature after about 2000 strikes or less. In oneembodiment, the faceplate 14 that is formed from an α-β Ti alloy andheat treated at or above its solvus temperature has 0% or lessdeflection from its original bulge and 0% or less deflection from itsoriginal roll curvature after about 2000 strikes or less.

FIG. 22 shows a phase diagram including lines representing HST-180 andT9S materials. HST-180 can be heat treated at a lower temperature(between 550° C. and 580° C.) than T9S (which can be treated betweenapproximately 600° C. and 650° C.) in some embodiments. In someembodiments, HST-180 can be heat treated at or above 550° C., at orabove 560° C., at or above 570° C., or at or above 580° C.

In other embodiments, HST-180 can be heat treated between 550° C. and1200° C. In some embodiments, HST-180 can be heat treated at or above590° C., at or above 600° C., at or above 610° C., at or above 620° C.,at or above 630° C., at or above 640° C., or at or above 650° C., at orabove 660° C., at or above 670° C., at or above 680° C., at or above690° C., at or above 700° C., at or above 710° C., at or above 720° C.,at or above 730° C., at or above 740° C., at or above 750° C., at orabove 760° C., at or above 770° C., at or above 780° C., at or above790° C., or at or above 800° C.

Referring now to FIG. 23, an experiment was performed to compare theeffect of various heat treatment temperatures on the faceplate 14 overthe course of 2,000 hits or ball strikes. The faceplates 14 were formedfrom HST-180 alloy. However, the data presented in FIG. 23 is limited tothe first 175 hits or ball strikes wherein the majority of the changestake place. The data between 175 and 2,000 hits or ball strikes plateausand follows a similar progression as the data displayed for 50 to 175hits. A first control club head assembly having an HST-180 faceplate wasnot heat treated. A second club head assembly was heated to 550° C.,which is above the solvus temperature of the HST-180 alloy, which isbetween 535° C. and 545° C. The measurement data provided in FIG. 23represent the percentage change in the radius of curvature of the bulgeand the roll dimensions compared to the original radius curvature. Asthe faceplate becomes more flat, the radius of curvature increases. Thefaceplate of the first club head assembly with no heat treatmentflattened significantly in both its roll and bulge dimensions within 50hits on a golf ball. However, the faceplate of the second club headassembly, which was heat treated to 550° C., maintained its curvaturesignificantly better than the first club head assembly after 2,000 hits.The main changes in roll and bulge dimensions occur within the first 50to 100 hits, as seen in FIG. 23. The HST-180 faceplate treated at 550°C. (second club head assembly) maintained its curvature better in bothroll and bulge dimensions after 2,000 hits than the first club headassembly having a faceplate 14 of untreated HST-180.

In one embodiment, the faceplate 14 formed from HST-180 and heat treatedat 550° C. remains within ˜5% deflection of its original roll curvatureand within ˜4% deflection of its original bulge curvature after 25strikes. In one embodiment, the faceplate 14 that is formed fromuntreated HST-180 remains within ˜27% deflection of its original rollcurvature and within ˜15% deflection of its original bulge curvatureafter about 25 strikes. The heat treatment reduces the deflection of theoriginal roll after 25 strikes by ˜22%. The heat treatment reduces thedeflection of the original bulge after 25 strikes by ˜11%.

In one embodiment, the faceplate 14 formed from HST-180 and heat treatedat 550° C. remains within 5% deflection of its original roll curvatureand within 4% deflection of its original bulge curvature after 50strikes. In one embodiment, the faceplate 14 that is formed fromuntreated HST-180 remains within ˜29% deflection of its original rollcurvature and within ˜14% deflection of its original bulge curvatureafter about 50 strikes. The heat treatment reduces the deflection of theoriginal roll after 50 strikes by ˜24%. The heat treatment reduces thedeflection of the original bulge after 50 strikes by ˜10%.

In one embodiment, the faceplate 14 formed from HST-180 and heat treatedat 550° C. remains within 6% deflection of its original roll curvatureand within 5% deflection of its original bulge curvature after 100strikes. In one embodiment, the faceplate 14 that is formed fromuntreated HST-180 remains within ˜31% deflection of its original rollcurvature and within ˜15% deflection of its original bulge curvatureafter about 100 strikes. The heat treatment reduces the deflection ofthe original roll after 100 strikes by ˜25%. The heat treatment reducesthe deflection of the original bulge after 100 strikes by ˜10%.

In one embodiment, the faceplate 14 formed from HST-180 and heat treatedat 550° C. remains within 7% deflection of its original roll curvatureand within 5% deflection of its original bulge curvature after 175strikes. In one embodiment, the faceplate 14 that is formed fromuntreated HST-180 remains within ˜34% deflection of its original rollcurvature and within ˜16% deflection of its original bulge curvatureafter about 175 strikes. The heat treatment reduces the deflection ofthe original roll after 175 strikes by ˜27%. The heat treatment reducesthe deflection of the original bulge after 175 strikes by ˜11%.

In one embodiment, the faceplate 14 formed from HST-180 and heat treatedat 550° C. remains within 5% deflection of its original roll curvatureand within 4% deflection of its original bulge curvature after 250strikes. In one embodiment, the faceplate 14 that is formed fromuntreated HST-180 remains within ˜27% deflection of its original rollcurvature and within ˜16% deflection of its original bulge curvatureafter about 250 strikes. The heat treatment reduces the deflection ofthe original roll after 250 strikes by ˜22%. The heat treatment reducesthe deflection of the original bulge after 250 strikes by ˜12%.

Type of Weld Affect Heat Treatment for α-β Ti alloy

As discussed above, the present invention is directed to a number of α-βtitanium alloy faceplates treated at or above the solvus temperature ofthe α-β titanium. The heat treatment of the faceplates helps maintaintheir original bulge and roll curvature after a 25, 50, 100, 250, or 500hits. In other words, the described heat treatment increases thedurability of the faceplates. The type of weld used to secure thefaceplate to the body can also affect the bulge/roll and stability ofthe α-β titanium alloy faceplate. Certain welds of α-β titanium alloysrequire certain heat treatments to relieve residual stress.

For example, FIG. 19 illustrates heat treatment of a plasma weld of anα-β titanium faceplate to a body. This example heat treatment couldapply to a faceplate formed from Ti9S. The faceplate is heat treatedabove 600° C. for one hour followed by a quick fan cooling step. Theplasma weld heat treatment process, graphed in FIG. 19, removes thermalstresses that build up in the heat affected zone (HAZ) around a plasmaweld. In particular, the exemplary process removes residual stresses inand around the plasma weld between a T9S faceplate and a club body. Inthe plasma weld stress relief process, α-β titanium faceplates arebrought to the solvus melt temperature and then held for 600° C. for onehour followed by a nitrogen gas blown onto the parts with a fan in orderto cool down to ambient temperature (quick cooling step). T9S faceplateswith plasm welds are treated in this manner to ensure the HAZ providesthe bulge/roll and stability characteristics as outlined above for T9Sfaceplates.

FIG. 19 also illustrates that a laser weld requires a different heattreatment of the Ti9S faceplate at the faceplate to body junction. Laserwelding uses more heat within a small, more precise region so there aremore residual stresses within the HAZ than the initial heat treatmentcan completely remove from the Ti9S faceplate HAZ. Therefore, as shownin FIG. 19, the HAZ is heat treated similarly to the plasma weld Ti9Sfaceplate for 1 hour at 600° C. However, for the laser weld HAZ heattreatment, the initial 1 hour treatment is followed by a 30-minute soakstep. In the soak step, the furnace heat source is turned off, but thechamber stays closed thereby allowing the laser weld HAZ to cool slowlyinstead of rapidly.

After the soaking step, the golf club with the laser weld Ti9S faceplateis treated with nitrogen gas in a fan cooling (quick cooling step). Insome embodiments, this quick-cooling step can last between 20-40minutes. By foregoing a soak step in a more heat laden laser weld,stresses are trapped in the α-β titanium alloy faceplate during thequick change in temperature and can cause a change in the shape aroundthe weld. By adding the soaking step to a laser weld-treated α-βtitanium alloy faceplate, the stresses migrate out of the HAZ allowingfor the faceplate to relax thereby retaining the initial bulge and rollshape for α-β titanium alloy faceplate such as Ti9S. Furthermore, thesoaking step also removes stress from the laser weld HAZ region therebyincreasing durability and allowing the laser weld/HAZ region to flexproperly for α-β titanium alloy faceplate such as Ti9S.

An α-β titanium alloy of the invention can be more susceptible to theBauschinger Effect where a build-up of stresses in polycrystallinematerials can increase yield strength at the expense of compressivestrength. This is particularly important when one side of the α-βtitanium alloy faceplate experiences a yield load while the oppositeside experiences a compressive load during impact. The stress relievingsteps as outlined above for plasma weld and laser weld of α-β titaniumalloy faceplate, such as Ti9S, are used to maintain the shape stabilityensuring more consistent bulge and roll profiles.

In FIG. 20, illustrates the bulge and roll stability of a laser weldedα-β titanium alloy faceplate, treated with and without the soak step.The tested faceplate comprises the Ti9S alloy. Although not illustrated,other α-β titanium alloy faceplates would react similarly to heattreatment. As shown in FIG. 20, after both 50 and 250 hits, the clubheads maintained below the max percentage deflection (less than 10%) ofbulge and roll when the laser weld α-β titanium alloy faceplate such asTi9S were treated with the additional soak step. Furthermore, FIG. 21demonstrates that club heads average nearly 830 more hits before failurewith laser welded α-β titanium alloy faceplate, such as Ti9S, when theadditional soak step was added after the heat treatment step. Therefore,as illustrated in FIGS. 19-21, two different types of weld HAZ zones(plasma vs. laser) for the same Ti9S faceplate require different heattreatments to ensure stability in bulge/roll as well as overalldurability until failure of the α-β titanium alloy faceplate. The laserweld of α-β titanium alloy faceplate, such as Ti9S, requires a soak stepafter heat treatment to ensure the surprising bulge/roll stability andnearly 50% increase in durability vs. non-α-β titanium alloy faceplates.

In addition to heat treating the weld around a Ti9S faceplate, the weldsaround other types of α-β titanium faceplates can be heat treated in asimilar manner. The exact temperatures and times for the heating,soaking (if necessary), and quick-cooling steps can differ based on thetype of α-β titanium used for the faceplate.

The invention provides, among other things, a method of forming a golfclub head assembly. Although the invention has been described in detailwith reference to certain preferred embodiments, variations andmodifications exist within the scope and spirit of one or moreindependent aspects of the invention as described.

Clause 1: A method of forming a golf club head assembly, the methodcomprising: (a) providing a faceplate formed from an α-β titanium alloy,the α-β titanium alloy comprising between 4 wt % to 20 wt % aluminum(Al), 2-3 wt % iron (Fe), and 0.25 wt % or less Silicon (Si); (b)aligning the faceplate with a recess of a club head; (c) welding thefaceplate to the club head; (d) heating the club head and the faceplateto a temperature that is greater than the solvus temperature of thefaceplate for a predetermined amount of time; and (e) allowing the clubhead and the faceplate to cool in an inert gas, wherein step (d) isperformed between 500° C. and 1200° C. for between 1 hour and 6 hours.

Clause 2: The method of clause 1, wherein the α-β titanium alloycomprises between 4 wt % to 18 wt % aluminum (Al).

Clause 3: The method of clause 1, wherein the α-β titanium alloycomprises between 5 wt % to 7 wt % aluminum (Al).

Clause 4: The method of clause 1, wherein the α-β titanium alloy furthercomprises less than 0.05 wt % carbon, less than 0.05 wt % copper (Cu),less than 0.05 wt % molybdenum (Mo), less than 0.05 wt % vanadium (V)and the remaining weight percent is titanium (Ti).

Clause 5: The method of clause 1, wherein the welding of step (c)includes a pulse plasma welding process.

Clause 6: The method of clause 1, wherein the welding of step (c)includes a laser welding process.

Clause 7: The method of clause 1, wherein the inert gas of step (e) isselected from the group consisting of nitrogen (N), argon (Ar), helium(He), neon (Ne), krypton (Kr), and xenon (Xe) or a compound gas thereof.

Clause 8: The method of clause 7, wherein the inert gas is nitrogen (N)or argon (Ar).

Clause 9: The method of clause 1, wherein the faceplate of step (a) hasa minimum thickness of 0.7 mm.

Clause 10: The method of clause 1, wherein step (d) includes heating theclub head and the faceplate between 500° C. and 1200° C. for between 1hour and 2 hours.

Clause 11: The method of clause 10, wherein heating the club head andthe faceplate includes heating the club head and the faceplate tobetween 550° C. and 580° C. for between 1 hour and 2 hours.

Clause 12: The method of clause 10, wherein heating the club head andthe faceplate includes heating the club head and the faceplate at orabove 535° C. for between 1 hour and 2 hours.

Clause 13: A method of forming a golf club head assembly, the methodcomprising: providing a faceplate formed from an α-β titanium alloy, theα-β titanium alloy comprising 4 wt % to 18 wt % aluminum (Al), 2-3 wt %iron (Fe), less than 0.25 wt % Silicon (Si); less than 0.05 wt % carbon,less than 0.05 wt % copper (Cu), less than 0.05 wt % molybdenum (Mo),less than 0.05 wt % vanadium (V) and the remaining weight percent istitanium (Ti); aligning the faceplate with a recess of a club head;welding the faceplate to the club head; after welding the faceplate,heating the club head and the faceplate to a temperature that is greaterthan the solvus temperature of the faceplate for a predetermined amountof time; and after heating the club head and the faceplate, allowing theclub head and the faceplate to cool in an inert gas environment.

Clause 14: The method of clause 13, wherein the α-β titanium alloycomprises between 5 wt % to 7 wt % aluminum (Al).

Clause 15: The method of clause 13, wherein welding the faceplateincludes a pulse plasma welding process.

Clause 16: The method of clause 13, wherein the welding of step (c)includes a laser welding process.

Clause 17: The method of clause 13, wherein the inert gas of step (e) isselected from the group consisting of nitrogen (N), argon (Ar), helium(He), neon (Ne), krypton (Kr), and xenon (Xe) or a compound gas thereof.

Clause 18: The method of clause 13, wherein heating the club head andthe faceplate includes heating the club head and the faceplate forbetween 1 hour and 6 hours.

Clause 19: The method of clause 13, wherein heating the club head andthe faceplate includes heating the club head and the faceplate to at orabove 535° C.

Clause 20: The method of clause 13, wherein heating the club head andthe faceplate includes heating the club head and the faceplate tobetween 500° C. and 1200° C. for between 1 hour and 2 hours.

1. A method of forming a golf club head assembly, the method comprising:(a) providing a faceplate formed from an α-β titanium alloy, the α-βtitanium alloy comprising between 4 wt % to 20 wt % aluminum (Al), 2-3wt % iron (Fe), and 0.25 wt % or less Silicon (Si); (b) aligning thefaceplate with a recess of a club head; (c) welding the faceplate to theclub head; (d) heating the club head and the faceplate to a temperaturethat is greater than the solvus temperature of the faceplate for apredetermined amount of time; and (e) allowing the club head and thefaceplate to cool in an inert gas, wherein step (d) is performed between500° C. and 1200° C. for between 1 hour and 6 hours.
 2. The method ofclaim 1, wherein the α-β titanium alloy comprises between 4 wt % to 18wt % aluminum (Al).
 3. The method of claim 1, wherein the α-β titaniumalloy comprises between 5 wt % to 7 wt % aluminum (Al).
 4. The method ofclaim 1, wherein the α-β titanium alloy further comprises less than 0.05wt % carbon, less than 0.05 wt % copper (Cu), less than 0.05 wt %molybdenum (Mo), less than 0.05 wt % vanadium (V) and the remainingweight percent is titanium (Ti).
 5. The method of claim 1, wherein thewelding of step (c) includes a pulse plasma welding process.
 6. Themethod of claim 1, wherein the welding of step (c) includes a laserwelding process.
 7. The method of claim 1, wherein the inert gas of step(e) is selected from the group consisting of nitrogen (N), argon (Ar),helium (He), neon (Ne), krypton (Kr), and xenon (Xe) or a compound gasthereof.
 8. The method of claim 7, wherein the inert gas is nitrogen (N)or argon (Ar).
 9. The method of claim 1, wherein the faceplate of step(a) has a minimum thickness of 0.7 mm.
 10. The method of claim 1,wherein step (d) includes heating the club head and the faceplatebetween 500° C. and 1200° C. for between 1 hour and 2 hours.
 11. Themethod of claim 10, wherein heating the club head and the faceplateincludes heating the club head and the faceplate to between 550° C. and580° C. for between 1 hour and 2 hours.
 12. The method of claim 10,wherein heating the club head and the faceplate includes heating theclub head and the faceplate at or above 535° C. for between 1 hour and 2hours.
 13. A method of forming a golf club head assembly, the methodcomprising: providing a faceplate formed from an α-β titanium alloy, theα-β titanium alloy comprising 4 wt % to 18 wt % aluminum (Al), 2-3 wt %iron (Fe), less than 0.25 wt % Silicon (Si); less than 0.05 wt % carbon,less than 0.05 wt % copper (Cu), less than 0.05 wt % molybdenum (Mo),less than 0.05 wt % vanadium (V) and the remaining weight percent istitanium (Ti); aligning the faceplate with a recess of a club head;welding the faceplate to the club head; after welding the faceplate,heating the club head and the faceplate to a temperature that is greaterthan the solvus temperature of the faceplate for a predetermined amountof time; and after heating the club head and the faceplate, allowing theclub head and the faceplate to cool in an inert gas environment.
 14. Themethod of claim 13, wherein the α-β titanium alloy comprises between 5wt % to 7 wt % aluminum (Al).
 15. The method of claim 13, whereinwelding the faceplate includes a pulse plasma welding process.
 16. Themethod of claim 13, wherein the welding of step (c) includes a laserwelding process.
 17. The method of claim 13, wherein the inert gas ofstep (e) is selected from the group consisting of nitrogen (N), argon(Ar), helium (He), neon (Ne), krypton (Kr), and xenon (Xe) or a compoundgas thereof.
 18. The method of claim 13, wherein heating the club headand the faceplate includes heating the club head and the faceplate forbetween 1 hour and 6 hours.
 19. The method of claim 13, wherein heatingthe club head and the faceplate includes heating the club head and thefaceplate to at or above 535° C.
 20. The method of claim 13, whereinheating the club head and the faceplate includes heating the club headand the faceplate to between 500° C. and 1200° C. for between 1 hour and2 hours.